Skip to main content

Full text of "The structure and development of mosses and ferns (Archegoniatae)"

See other formats


ii;ili:u:i 



I 



; I ! I r : I r  



I 



liiii 



iiiiiiii; 



THE STRUCTURE AND DEVELOPMENT 
OF MOSSES AND FERNS 



fl^^^ 



a9 "* o 



The Structure and Development 

of 

Mosses and Ferns 

i^Archegoniatae) 



THIRD EDITION, REVISED AND ENLARGED 



BY 



DOUGLAS HO'UQHTON CAMPBELL, Ph.D. 

Professor of Botany 
LfiwAnd Stanford Jjnior UnfvejvSity 

■J < t) •' '^ * 

1 » .^ .J - . ^' 









• - . 



THE MACMILLAN COMPANY 

London : Macmillan & Co., Ltd. 
1918 

All ri^hfs reserved 



;^/r 



Copyright, 1905 
By the MACMILLAN COMPANY 

^ w ■* * >* ► 

<  c ( •« ^ • • 

< / Srt up ^rM ere(?trotyir<^a 

, ' / ' Published, September, looi 
, , \ Rep'-in^^ed JuV. 1913 

' . - '^< 

c 






PREFACE TO THE SECOND EDITION 

Since the first edition of the present work was pub- 
lished, the number of important investigations on the struc- 
ture and development of the Archegoniatse has been so 
great that it has been found necessary to recast entirely 
certain portions of the work, this being especially the case 
with the chapters dealing with the eusporangiate Ferns. 
The whole book, however, has been carefully revised, and a 
good deal of new matter introduced, including two special 
chapters on the geological history of the Archegoniates, 
and the significance of the alternation of generations. 

Some of the new material incorporated in the present 
work is published for the first time; but much of it is based 
upon papers published by the writer since the first edition 
was published. The work of other investigators has been 
freely drawn upon, and acknowledgment has been made in 
all cases where statements or illustrations have been bor- 
rowed from other sources than the writer's own inves- 
tigations. 

The large number of recent books and papers on the 
Archegoniates has involved an entire revision of the bibli- 
ography, which has been materially augmented. It is 
hoped that it will be found to be a fairly complete list of 
the more recent works bearing upon the structure of the 
Archegoniates. 

The results of more recent investigations have necessi- 
tated, in some cases, a modification of certain views ex- 
pressed by the author in the earlier edition. In other 
cases, however, his views have been confirmed as the result 
of more complete knowledge of certain forms. 



PREFACE 

In view of the decidedly unsettled state of nomenclature 
at the present time, it has seemed best to maintain a some- 
what conservative attitude in this matter, and this will ex- 
plain the retention of some familiar names, which perhaps 
are not in accord with a strict law of priority. 

The author is especially indebted to Professor E. C. 
Jeffrey and to Dr. W. R. Shaw, for valuable preparations 
which were of great assistance in the preparation of the 
chapters on the Ferns. Thanks are also due one of my 
students, Mr. H. B. Humphrey, for the preparation of the 
drawings for figures 43, 44 and 47. 

The author also would express his thanks to Professor 
D. S. Johnson of Johns Hopkins University for kindly re- 
vising a portion of the bibliography, and to Professor G. 
J. Peirce of Stanford University for valuable assistance in 
reading part of the proof. 



DOUGLAS HOUGHTON CAMPBELL. 



Stanford University, 
April, 1905. 



VI 



PREFACE TO THE THIRD EDITION 

In the second edition of the "Mosses and Ferns," the original 
text was carefully revised, and a good deal of it was rewritten. 
At the same time considerable new matter was added. In 
preparing the present edition of the book, it has not seemed 
necessary to change the body of the text, the new material being 
given in the form of an appendix. 

Since the publication of the last edition, as might be expected, 
numerous contributions have been made to the literature of the 
Morphology and Classification of the Archegoniates. Among 
these contributions are several publications by the writer. These 
are for the most part based upon collections of tropical Liverworts 
and Ferns made by the writer, including some new and rare 
species of the Indo-Malayan region. 

A summary of the more important results of these studies as 
well as those of other investigators is added to the text in the 
form of an appendix, in which the new material is arranged 
under the Chapter headings which deal with the allied topics 
in the main text. In the appendix, also, certain errors of state- 
ment and reference in the original text have been corrected. 

The numerous additions in the literature on the subject have 
necessitated a complete revision of the bibliography, which has 
been very considerably enlarged. 

It is hoped that with the appendix and augmented bibliog- 
raphy the book will prove a satisfactory statement of our present 
knowledge of the structure and development of the Archegoniate 

Plants. 

DOUGLAS HOUGHTON CAMPBELL. 

Stanford University, 
January, 1918. 



vu 



CO NTENTS 

CHAPTER I 
Introduction = i 

CHAPTER H 
MusciNE^ (Bryophyta) — Hepatic^ — Marchantiales 8 

CHAPTER HI 
The Jungermanniales 72 

CHAPTER IV 
The Anthocerotes » « o . . . 120 

CHAPTER V 
The Mosses (Musci) : Sphagnales — Andre^eales 160 

CHAPTER VI 
The Bryales • , 188 

CHAPTER VII 
The Pteridophyta — Filicine^ — Ophioglossace^ 229 

CHAPTER VIII 

Marattiales ^JZ 

CHAPTER IX 
FiLiciNE^ Leptosporangiat^ 305 

CHAPTER X 
The Homosporous Leptosporangiat^ (Filices) 346 

CHAPTER XI 
Leptosporangiat^ Heterospore^ ( Hydro pterides) 396 

CHAPTER XII 
Equisetine^ 443 

CHAPTER XIII 
Lycopodine^ 483 

CHAPTER XIV 
Isoetace^ 536 

CHAPTER XV 
The Nature of the Alternation of Generations 562 

CHAPTER XVI 
Fossil Archegoniates 576 

CHAPTER XVII 
Summary and Conclusions 592 

ix 



CONTENTS 

Appendix 607 

Bibliography 645 

Index 681 



CHAPTER I 

INTRODUCTION 

Under the name Archegoniatse are included a large number 
of plants which, while differing a good deal in many structural 
details, still agree so closely in their essential points of 
structure and development as to leave no room for doubting 
their close relationship. Besides the Bryophytes and Pteri- 
dophytes, which are ordinarily included under this head, the 
Gymnospermse or Archespermge might very properly be also 
embraced here, but we shall use the term in its more restricted 
meaning. 

The term Archegoniat^e has been applied to these plants 
because the female reproductive organ or archegonium is 
closely alike, both in origin and structure, in all of them. This 
is a multicellular body, commonly flask-shaped, and either 
entirely free or more or less coherent with the tissues of the 
plant. In all cases there is an axial row of cells developed, of 
which the lowxst forms the egg. The others become more or 
less completely disorganized and are discharged from the 
archegonium at maturity. Among the Algae there is no form 
at present known in which the female organ can be certainly 
compared to the archegonium, although the oogonium of the 
Characese recalls it in some respects. 

The antheridium or male organ of the Archegoniatse, while 
it shows a good deal of similarity in all of them, still exhibits 
much more variation than does the archegonium, and is more 
easily comparable with the same organ in the Algae, especially 
the Characese. Like the archegonium it may be entirely free, 
or even raised on a long pedicel ; or it may be completely sunk 
in the tissue of the plant, or even be formed endogenously. It 
usually consists of a single outer layer of cells containing 



2 MOSSES AND FERNS chap. 

chlorophyll, and these enclose a mass of small colourless cells, 
the sperm cells, each of which gives rise to a single ciliated 
spermatozoid. The development of the latter is very uniform 
throughout the Archegoniatse, and differs mainly from the 
same process in the higher green Algae, especially the Characeae, 
in the larger amount of nuclear substance in the spermatozoids 
of the former. 

Fertilisation is only effected when the plants with ripe 
sexual organs are covered with water. The absorption of 
water by the mature sexual organs causes them to open, and 
then, as the spermatozoids are set free, they make their way 
through the water by means of their cilia and enter the open 
archegonium, into which they penetrate to the egg. The 
sexual cells do not differ essentially from those of the higher 
Algae, and point unmistakably to the origin of the Arche- 
goniatae from similar aquatic forms. Indeed all of the 
Archegoniatae must still be considered amphibious, inasmuch 
as the gametophyte or sexual plant is only functional when 
partially or completely submerged. 

Non-sexual gonidia are known certainly only in Aneura, 
one of the lower Liverworts, but special reproductive buds or 
gemmae, both unicellular and multicellular, are common in 
many forms. 

A very marked characteristic of the whole group is the 
sharply-marked alternation of sexual and non-sexual stages. 
The sexual plant or gametophyte varies much in size and 
complexity. It may be a simple flat thallus comparable in 
structure to some Algae, and not superior to these in com- 
plexity so far as the vegetative parts are concerned. In others 
it becomes larger and shows a high degree of differentiation. 
Thus among the Liverworts the Marchantiaceae, while the 
gametophyte still retains a distinctly thalloid form, still show 
a good deal of variety in the tissues of which the thallus is 
composed. In others, e.g., the true Mosses, the gametophyte 
has a distinct axis and leaves, and in the higher ones the tissues 
are well differentiated for special functions. The gametophyte 
itself may show two well-marked phases, the protonema and 
the gametophore. The former is usually filamentous, and 
arises directly from the germinating spore; and upon the 
protonema, as a special branch or bud, the much more complex 
gametophore is borne. Often, however, as in many thallose 



I INTRODUCTION 3 

Liverworts and Pteridophytes, the protonema is not clearly 
distinguishable from the gametophore, or may be completely 
suppressed. In the Pteridophytes the gametophyte is, as a 
rule, much simpler than in the Bryophytes, resembling most 
nearly the less specialised forms of the latter. In the so-called 
heterosporous Pteridophytes the gametophyte becomes ex- 
tremely reduced and the vegetative part almost entirely sup- 
pressed, and its whole cycle of development may, in extreme 
cases, be completed within twenty- four hours or even less. 

The non-sexual generation, or "sporophyte," arises normally 
from the fertilised Qgg, but may in exceptional cases develop as 
a bud from the gametophyte. In its simplest form all the 
cells of the sporophyte, except a single layer upon the out- 
side, give rise to spores, but in all the others there is developed 
a certain amount of vegetative tissue as well, and the sporo- 
phyte becomes to a limited extent self-supporting. In the 
higher Bryophytes the sporophyte sometimes exceeds in size 
the gametophyte, and develops an elaborate assimilative system 
of tissues, abundantly supplied wnth chlorophyll and having an 
epidermis with perfect stomata; but even the most complex 
moss-sporogonium is to a certain extent dependent upon the 
gametophyte with which it remains in close connection by 
means of a special absorbent organ, the foot. In these highly 
developed sporogonia the sporogenous tissue occupies but a 
small space, by far the greater part of the tissue being purely 
vegetative. 

In the Pteridophytes a great advance is made in the sporo- 
phyte beyond the most complex forms found among the 
Bryophytes. This advance is twofold, and consists both in an 
external differentiation and a more perfect development of the 
tissues. The earliest divisions of the embryo resemble very 
closely those of the Bryophyte sporogonium, but at an early 
stage four distinct organs are usually plainly distinguishable, 
viz., stem, leaf, root, and foot. The last corresponds in some 
degree to the same organ in the moss-sporogonium, and like it 
serves as an absorbent organ by which the young sporophyte 
is supplied with nourishment from the gametophyte. In short, 
the young sporophyte of the Pteridophyte, like that of the 
Bryophyte, lives for a time parasitically upon the gametophyte. 
Sooner or later, however, the sporophyte becomes entirely 
independent. This is effected by the further growth of the 



4 MOSSES AND FERNS chap. 

primary root, which brings the young sporophyte into direct 
communication with the earth. The primary leaf, or cotyle- 
don, enlarges and becomes functional, and new ones arise 
from the stem apex. Usually by the time this stage is reached 
the gametophyte dies and all trace of it soon disappears. In 
some of the lower forms, however, the gametophyte is large 
and may live for many months, or even years, when not 
fecundated, and even when the sporophyte is formed, the 
prothallium (gametophyte) does not always die immediately, 
but may remain alive for several months. The spore-forming 
nature of the sporophyte does not manifest itself for a long 
time, sometimes many years, so that spore-formation is much 
more subordinate than in the highest Bryophytes. With few 
exceptions the spores are developed from the leaves and in 
special organs, sporangia. In the simplest case, e. g., Ophio- 
glossum, the sporangia are little more than cavities in the tissue 
of the sporiferous leaf, and project but little above its surface. 
Usually, however, the sporangia are quite free from the leaf 
and attached only by a stalk. These sporangia are in the 
more specialised forms of very peculiar and characteristic 
structure, and are of great importance in classification. 

Corresponding to the large size and development of special 
organs in the sporophyte of the Pteridophytes, there is a great 
advance in the specialisation of the tissues. All of the forms 
of tissue found in the Spermaphytes occur also among the 
Pteridophytes, w^hich indeed, so far as the character of the 
tissues of the sporophyte is concerned, come much nearer to 
the former than they do to the Bryophytes. This is especially 
true of the vascular bundles, which in their complete form are 
met with first in the sporophyte of the Pteridophyta. In size, 
too, the sporophyte far exceeds that of the highest Mosses; 
w^hile in these the sporogonium seldom exceeds a few centime- 
tres in extreme height, in some Ferns it assumes tree-like pro- 
portions with a massive trunk lo to 15 metres in height, with 
leaves 5 to 6 metres in length. 

In the formation of the spores all of the Archegoniatse 
show great uniformity, and this extends, at least as regards 
the pollen spores, to the Spermatophytes as well. In all cases 
the spores arise from cells which at first form a solid tissue 
arising from the division of a single primary cell, or group of 
cells (Archesporium). These cells later become more or less 



I INTRODUCTION 5 

completely separated, and each one of these so-called "spore 
mother cells," by division into four daughter cells, forms the 
spores. The young spores are thin walled, but later the wall 
becomes thicker and shows a division into two parts, one inner 
layer, which generally shows the cellulose reaction and is called 
the endospore (intine), and an outer more or less cuticularised 
coat, the exospore (exine). In addition a third outer coat 
(perinium, epispore) is very generally present. As the spore 
ripens there is developed within it reserve food materials in 
the form of starch, oil, and albuminous matter, and quite 
frequently chlorophyll is present in large quantity. Some 
spores retain their vitality but a short time, those of most 
species of Equisetum and Osiminda, for example, germinating 
with difficulty if kept more than a few days after they are 
shed, and very soon losing their power of germination com- 
pletely. On the other hand, some species of Marsilia have 
spores so tenacious of life that they germinate perfectly after 
being kept for several years. 

From the germinating spore arises the gametophyte bear- 
ing the sexual organs. Both archegonia and antheridia may 
be borne upon the same plant, or they may be upon separate 
ones. From the fertilised egg within the archegonium is pro- 
duced the sporophyte or non-sexual generation, and from the 
spores which it produces arise the sexual individuals again, 
thus completing the cycle of development. 

On comparing the lower Archegoniates with the higher 
ones, it is at once evident that the advance in structure consists 
mainly in the very much greater development of the sporophyte. 
In the Bryophytes, as a class, the gametophyte is more impor- 
tant than the sporophyte, the latter being, physiologically, 
merely a spore-fruit, which in many forms, e. g., Sphagnum, is 
of relatively rare occurrence. The gametophyte in such forms 
is perennial, and the same plant may produce a large number of 
sporogonia, and at long intervals. The sporophyte in such 
forms is small and simple in structure, and its main function 
is spore formation, as it has but little power of independent 
growth. In the Pteridophytes, on the other hand, the gameto- 
phyte (prothallium) rarely produces more than one sporophyte, 
and as soon as this, by the formation of a root and leaf, becomes 
self-supporting, the gametophyte dies. In short, the sole 



6 MOSSES AND FERNS chap. 

function of the latter in most of them is to support the sporo- 
phyte until it can take care of itself. 

When the lower Pteridophytes are compared with the more 
specialised ones, a similar difference is found. In the lower 
forms, like the Marattiacese and Equisetacese, the gametophyte 
is relatively large and long-lived, and closely resembles certain 
Liverworts. In these forms a considerable time elapses before 
sexual organs are produced, and in artificial cultures of the 
Marattiacese a year or more sometimes passes before archegonia 
are formed. These prothallia, too, multiply by budding, much 
as the Liverworts do. In case no archegonia are fecundated 
the prothallium may grow until it reaches a length of three or 
four centimetres, and resembles in a most striking manner a 
thallose Liverwort. In such large prothallia it is not unusual 
for more than one archegonium to be fecundated, although 
usually only one of the embryos comes to maturity, and the 
prothallium may continue to live for some time after the 
sporophyte has become independent. Usually, however, as 
soon as an archegonium is fertilised, the formation of new ones 
ceases, and as soon as the sporophyte is fairly rooted in the 
ground the prothallium dies. 

In most of the lower Pteridophytes the prothallia are 
monoecious, but in the more specialised ones are markedly 
dioecious. When this is least marked the males and females 
differ mainly in size, the latter being decidedly larger; in the 
more extreme cases the difference is much more pronounced 
and is correlated with a great reduction in the vegetative part 
of the gametophyte of both males and females. This reaches 
its extreme phase in the so-called heterosporous forms. In 
these the sex of the gametophyte is already indicated by the 
character of the spore. Two sorts of spores are produced, large 
and small, which produce respectively females and males. In 
all of the heterosporic Pteridophytes the reduction of the vege- 
tative part of the gametophyte is very great, especially in the 
male plants. Here this may be reduced to a single quite 
functionless cell, and all the rest of the plant is devoted to the 
formation of the single antheridium. In the female plants the 
reduction is not so great; and although sometimes but one 
archegonium is formed, there may be in some cases a consider- 
able number, and owing to the large amount of nutritive 
material in the spore, in case an archegonium is not fertilised. 



I INTRODUCTION 7 

the prothallium, even if it does not form chlorophyll, may grow 
for a long time at the expense of the food materials that nor- 
mally are used by the developing embryo. In strong contrast 
to the slow growth and late development of the reproductive 
organs in the homosporous forms, most of the heterosporous 
Pteridophytes germinate very quickly. The Marsiliacese, in 
which the female prothallium is extremely reduced, show the 
opposite extreme. Here the whole time necessary for the 
germination of the spores and the maturing of the sexual 
organs may be less than twenty- four hours, and within three or 
four days more the embryo is completely developed. 

That heterospory has arisen independently in several widely 
separated groups of Pteridophytes is plain. The few genera 
that still exist are readily separable into groups that have 
comparatively little in common beyond possessing two sorts of 
spores; but each of these same forms shows much nearer 
affinities to certain widely separated homosporous groups. 

In some of the heterosporous forms the first divisions in the 
germinating spore take place while it is still within the sporan- 
gium, and may begin before the spore is nearly fully devel- 
oped. In other cases the sporangia become detached when 
ripe, and the spore (or spores), still surrounded by the spo- 
rangium, falls away from the sporophyte before germination 
begins. In these respects the heterosporous Pteridophytes 
show the closest analogy with the similar processes among the 
lower Spermatophytes, where it has been shown in the most 
conclusive manner that the ovule with its enclosed embryo-sac 
is the exact morphological equivalent of the macrosporangium 
of Selaginella or Azolla, for example, and that the seed is 
simply a further development of the same structure. 



CHAPTER II 

MUSCINAE (BRYOPHYTA)— HEPATICAE— MARCHANTIALES 

The first division of the Archegoniatse, the Muscinese or 
Bryophyta, comprises the three classes, Hepaticse or Liverworts, 
the Musci or Mosses and the Anthocerotes. In these as a rule 
the gametophyte is much more developed than the sporophyte, 
and indeed in many forms the latter is very rarely met with. 
They are plants of small size, ranging in size from about a milli- 
metre in length to 30 centimetres or more. A few of them are 
strictly aquatic, i. e., Riella and Ricciocarpiis among the Hepat- 
icse, and Fontinalis of the Mosses; but most of them are 
terrestrial. A favourite position for many is the trunks of 
trees or rocks. Many others grow upon the earth. They 
vegetate only when supplied with abundant moisture, and 
 some forms are very quickly killed if allowed to become dry; 
but those species which grow in exposed places may be com- 
pletely dried up without suffering, and some of those that 
inhabit countries where there are long dry periods may remain 
in this condition for months without losing their vitality, 
reviving immediately and resuming growth as soon as they are 
supplied with the requisite moisture. 

The germinating spores usually produce a more or less 
well-marked "protonema," from which the gametophore arises 
secondarily. The protonema sometimes is persistent and 
forms a dense conferva-like growth, but more commonly it is 
transient and disappears more or less completely after the 
gametophore is formed. No absolute line, however, can be 
drawn between protonema and gametophore, as the former 
may arise secondarily from the latter, or even from the sporo- 
phyte. With very few exceptions, e.g., Buxhaiimia, the game- 
tophyte of the Muscinese is abundantly supplied with chloro- 

8 



CH. II MUSCINE^— HEPATIC.^— MARCH ANTI ALES 9 

phyll, and therefore capable of entirely independent growth. 
No true roots are found, but rhizoids are generally present in 
great numbers, and these serve both to fasten the plant to the 
substratum and also to supply it with nutriment. 

The form of the gametophyte varies much. In the simplest 
Hepaticas, like Anciira and Pcllia, it is a flat, usually dichoto- 
mously branched thallus composed of nearly or cjuite uniform 
cells, without traces of leaves or other special organs. From 
this simplest type, which is quite like certain Algse, differentia- 
tion seems to have proceeded in two directions; in the first 
instance the plant has retained its thallose character, but there 
has been a specialisation of the tissues, as we see in the higher 
Marchantiaceae. In the second case the differentiation has 
been an external one, the thallose form giving place to a dis- 
tinct leafy axis. This latter form reaches its completest 
expression in the higher Mosses, where it is accompanied by a 
high degree of specialisation of the tissues as well. The 
growth is usually from a single apical cell, which varies a good 
deal in form among the thallose Hepaticse, but in the foliose 
Hepaticse and Mosses is with few exceptions a three-sided 
pyramid. 

The gametophyte of the Muscinese frequently is capable of 
rapid multiplication, w^hich may occur in several ways. Where 
a filamentous protonema is present this branches extensively, 
and large numbers of leafy axes may be produced as buds from 
it. Sometimes these buds are arrested in their development 
and enter a dormant condition, and only germinate after a 
period of rest. Another very common method of multiplica- 
tion is for the growing ends of the branches of a plant to 
become isolated by the dying aw^ay of the tissues behind them, 
so that each growing tip becomes the apex of a new plant. 
Very common in the Hepatic?e, but less so in the Mosses, is the 
formation of gemmae or special reproductive buds. These are 
produced in various ways, the simplest being the separation of 
single cells, or small groups of cells, from the margins of the 
leaves. In the case of Aneura midtifida they are formed within 
the cells and discharged in a manner that seems to be identical 
with that of the zoospores of many Algae. Again, multicellu- 
lar gemmae of peculiar form occur in several of the Hepaticae, 
e.g., Blasia, Marchantia, wdiere they occur in special receptacles, 



10  MOSSES AND FERNS chap. 

and amonr the Mosses similar ones are common in Tetraphis 
and some other genera. 

The archegonia of all the Muscineae agree closely in their 
earlier stages, but differ more or less in the different groups at 
maturity. In all cases the archegonium arises from a single 
superficial cell, in which three vertical walls are formed that 
intersect so as to form an axial cell and three peripheral ones. 
From the axial cell develop the &gg, canal cells, and cover cells 
of the neck, and from the peripheral cells the wall of the venter 
and the outer neck cells. In all Muscineae except the Antho- 
cerotes the archegonium mother cell projects above the sur- 
rounding cells, but in the latter the mother cell does not project 
at all, and the archegonium remains completely sunken in the 
thallus. In all other forms the archegonium is nearly or quite 
free, and usually provided with a short pedicel. This is espe- 
cially marked in the Mosses, where the lower part of the arche- 
gonium is as a rule much more massive than in the Hepaticae. 

The most marked difference, however, between the arche- 
gonium of the Hepaticse and Mosses is in the history of the 
cover cell or uppermost of the axial row of cells of the young 
archegonium. This in the former divides at an early period 
into four nearly equal cells by vertical walls, the resulting cells 
either remaining undivided, or undergoing one or two more 
divisions ; but in the Mosses this cell functions as an apical cell, 
and to its further growth and division nearly the whole growth 
of the neck is due. 

The antheridia, except in the Anthocerotes, also arise from 
single superficial cells, and while they differ much in size and 
form, are alike in regard to their general structure. The 
antheridium always consists of two parts; a stalk or pedicel, 
which varies much in length, and the antheridium proper, made 
up of a single layer of superficial cells and a central mass of 
small sperm cells. The former always contain chloroplasts, 
which often become red or yellow at maturity. The sperm 
cells have no chlorophyll, but contain abundant protoplasm and 
a large nucleus, which latter forms the bulk of the body of the 
spermatozoid found in each sperm cell of the ripe antheridium. 
The spermatozoids are extremely minute filiform bodies, 
thicker behind and provided with two fine cilia attached to 
the forward end. Adhering to the thicker posterior end there 
may usually be seen a delicate vesicle, which represents the 



II MUSCINEAi—HEPA TIC^— MARCH ANTI ALES ii 

remains of the cell contents not used up in the formation of 
the spermatozoid. 

When the ripe sexual organs are placed in water their 
outer cells absorb water rapidly and become strongly distended, 
while the central cells, i.e., the canal cells of the archegonium, 
and the sperm cells, whose walls have become mucilaginous, 
have their walls dissolved. The swelling of the mucilage 
derived from the walls of the central cells, combined with the 
pressure of the strongly distended outer cells, finally results 
in the bursting open of both archegonium and antheridium. 
In the former, by the forcing out of the remains of the canal 
cells an open channel is left down to the ^gg, which has been 
formed by the contracting of the contents of the lowest of the 
axial cells. In the antheridium the walls of the sperm cells 
are not usually completely dissolved at the time the anther^ 
idium opens, so that the spermatozoids are still surrounded 
by a thin cell wall when they are first discharged. This soon 
is completely dissolved, and the spermatozoid then swims 
away. The substance discharged by the archegonium exer- 
cises a strong attraction upon the spermatozoids, which are 
thus directed to the open mouth of the archegonium, which 
they enter. Only a single one actually enters the Qgg, w^here 
it fuses with the egg-nucleus, and thus effects fertilisation. 
The tgg immediately secretes a cellulose wall about itself, and 
shortly after the fusion of the nuclei is complete the first 
segmentation of the young embryo takes place. 

The origin of the sexual organs is from a single cell, but 
the position of this cell varies much. In the thallose Hepaticas 
it is a superficial cell, formed from a segment of the apical cell 
either of a main axis or of a special branch. In most of the 
foliose Hepaticse and the Mosses, the apical cell of the shoot 
becomes itself the mother cell of an archegonium, and of course 
with this the further growth of the axis is stopped. The 
antheridia in the foliose Hepatic?e are usually placed singly 
in the axils of more or less modified leaves, but in most Mosses 
the antheridia form a terminal group. ]\Iixed with the sexual 
organs are often found sterile hair-like organs, paraphyses, 
often of very characteristic forms. In the foliose Hepaticse 
and most Mosses, the archegonia are often surrounded by 
specially modified leaves, and in the former there is also an 
inner cup-like perichastium formed from the tissue surrounding 



12 MOSSES AND FERNS chap. 

the archegonia. In the thallose Hepaticae, both antheridia and 
archegonia are generally enclosed by a sort of capsule, similar 
to the perichsetium of the foliose forms formed by the growth 
of the tissue of the thallus immediately surrounding them. 

The Asexual Generation 
{Sporophyte, Sporophore, Sporogonium) 

The sporophyte of the Muscinese is usually known as the 
sporogonium, and, as already stated, never becomes entirely 
independent of the gametophyte. After the first divisions are 
completed there is at an early period, especially in the 
Hepaticse, a separation of the spore-producing tissue or arche- 
sporium, all the cells of which may produce spores, as in Riccia 
and the Mosses, or a certain number form special sterile cells 
which either undergo little change and serve simply as nourish- 
ment for the growing spores, as in Sphccrocarpus, or more 
commonly assume the form of elongated cells, — elaters, which 
assist in scattering the ripe spores. 

Classification 
Class I. Hepaticce {Liverworts) 

The protonema is either rudimentary or wanting, and 
usually not sharply differentiated from the gametophore. The 
gametophore is, with the exception of Haplomitrium and Calo- 
hryum, strongly dorsi ventral, and may be either a (usually 
dichotomously) branched thallus or a stem with two or three 
rows of leaves. Non-sexual multiplication of the gametophyte 
by the separation of ordinary branches, or by special reproduc- 
tive bodies, gonidia (Aneiira multiUda) or gemmae — (many 
foliose Jungermanniaceae, Blasia, Marchantia, etc.). The 
sporogonium (except in Anthocerotes) remains within the 
enlarged venter (calyptra) of the archegonium until the 
spores are ripe. Before the spores are shed the sporogonium 
generally breaks through the calyptra by the elongation of the 
cells of the stalk or seta. All the cells of the archesporium 
may produce spores, or part of them may produce sterile cells 
or elaters. 



II MUSCINEAi— HEPATIC JE— MARCH ANTI ALES 13 

Class II. Anthoccrotcs. 

Gametophyte, a simple thallus, or sometimes showing a 
trace of leaf-formation in Dcndroccros; a single large chloro- 
plast, containing a pyrenoid, in each cell ; archegonium sunk 
in the thallus, the antheridium endogenous; sporophyte large, 
with long continued basal growth ; sporogenous tissue derived 
from the outer tissue (amphithecium) of the embryo. 

Class III. Miisci (Mosses) 

The gametophyte shows a sharp separation into protonema 
and gametophore. The protonema arises primarily from the 
germinating spore, and may be either a flat thallus or more 
commonly an extensively branching confervoid growth. 
Upon this as a bud the gametophore arises. This has always 
a more or less developed axis about w^hich the leaves are 
arranged in two, three, or more rows. A bilateral arrange- 
ment of the leaves is rare, and the stems branch monopodially. 
The asexual multiplication is by the separation of branches 
through the dying away of the older tissues, or less commonly 
by special buds or gemmse. Both stem and leaves have the 
tissues more highly differentiated than is the case in the 
Hepaticse. The archesporium is developed as a rule later 
than is the case in the Hepaticse, and within is a large central 
mass of tissue, the columella, which persists until the capsule 
is ripe. In most cases there is a large amount of assimilative 
tissue in the outer part of the capsule, and the epidermis at its 
base is provided with stomata. The growing embryo breaks 
through the calyptra at an early stage, and the upper part is 
in most cases carried up on top of the elongating sporogonium. 
In very much the greater number of forms the top of the cap- 
sule comes away as a lid (operculum). 

THE HEPATIC^ 

The Hepaticai show many evidences of being a primitive 
group of plants, and for this reason a thorough knowledge of 
their structure is of especial importance in studying the origin 
of the higher plants, as it seems probable that all of these 
are derived from Liverwort-like forms. On comparing the 



14 MOSSES AND FERNS chap. 

Hepaticse with the Mosses one is at once struck with the very 
much greater diversity of structure shown by the former group, 
although the number of species is several times greater in the 
latter. On the one hand, the Hepaticse approach the Algae, 
the thallus of the simpler forms being but little more compli- 
cated than that of many of the higher green Algae. On the 
other hand, these same simpler Liverworts resemble in a most 
striking manner the gametophyte of the Ferns. The same 
difference is observed in the sporophyte. This in the simplest 
Liverworts, e. g., Riccia, is very much like the spore-fruit of 
Coleochccfe, one of the confervoid green Algge ; on the other 
hand, the sporogonium of Anthoceros shows some most 
significant structural affinities with the lower Pteridophytes. 
The simplest form of the gametophyte among the Hepaticse 
is found in the thallose Jungermanniacese and Anthocerotes. 
In such forms as Aneura (Fig. 38) and Anthoceros (Fig. 55) 
the thallus is made up of almost perfectly uniform chlorophyll- 
bearing tissue, fastened to the earth by means of simple 
rhizoids. In forms a little more advanced, e. g., Metzgeria, 
Pallavicinia (Fig. 38), there is a definite midrib present. 
From this stage there has been a divergence in two directions. 
In one series, the Marchantiacese, there has been a specialisa- 
tion of the tissues, with a retention of the thallose form of 
the plant. In Riccia (Figs. 1-9) we find two clearly marked 
regions, a dorsal green tissue, with numerous air-spaces, and a 
ventral compact colourless tissue. In the higher Marchantia- 
cese (Fig. 16) this is carried still further, knd the air-chambers 
often assume a definite form, and a distinct epidermis with 
characteristic pores is formed. In the Marchantiacese also 
ventral scales or leaf-like lamellse are developed, and rhizoids 
of two kinds are present. Starting again from the flat, simple 
thallus of Anciira there has been developed the leafy axis of the 
more specialised Jungermanniacese. Between the latter and 
the strictly thallose forms are a number of interesting inter- 
mediate forms, like Blasia and Fossornhronia, where the first 
indication of the two dorsal rows of leaves is met with ; and in • 
Blasia at least the rudiments of the ventral row of small leaves 
(amphigastra) usually found in the foliose forms are present. 
The tissues of the Liverworts are very simple, and consist 
for the most part of but slightly modified parenchyma. Occa- 
sionally (Preissia) thickened sclerenchyma-like fibres occur, 



II MUSCINE^—HEPA TICJE— MARCH ANT I ALES 1$ 

but these are not common. Mucilage cells of various kinds 
are common. The secreting cells may be hairs on the ventral 
surface, and especially developed near the apex, where the 
mucilaginous secretion serves to protect against drying up ; or 
they may be isolated (Marchautia) or rows of cells (Cono- 
cephahis) within the tissue of the thallus. 

The growth of the gametophyte is usually due to the 
division of a single apical cell. In some of the thallose forms, 
e.g., Marchantiaceas, Anthocerotes, a single initial cell is not 
always to be recognised in the older thallus, but in these forms 
a single initial always appears to be present in the earlier stages. 
In the Jungermanniacese, howxver, a single apical cell is always 
distinguishable, but varies a good deal in form in different 
genera, at least among the thallose forms, or even in the same 
genus. Among the foliose Jungermanniacese it always has 
the form of a three-sided pyramid. From the apical cell seg- 
ments are cut off in regular succession, and the first divisions 
of the segments also show much regularity, and often bear a 
definite relation to the tissues of the older parts. 

The Sexual Organs 

The archegonium is always traceable to a single cell, but 
the position of the mother cell is very different in different 
genera. In the simplest cases, e.g., Riccia, Sphcerocarpns 
(Figs. 2, 29), the mother cell is formed from a superficial cell 
of one of the youngest dorsal segments of the apical cell, close 
to the growing point of an ordinary branch of the thallus, 
whose growth is in no way affected by the formation of arche- 
gonia. In such forms the archegonia stand alone, and about 
each is developed a sort of involucre by the growth of a ring 
of cells immediately surrounding the archegonium rudiment. 
In other cases the archegonia are found in groups, e. g., Palla- 
vicinia (Fig. 38), separated by spaces where no archegonia are 
found. Here each group of archegonia has a common invol- 
ucre. In Aneiira and most of the higher Marchantiacese the 
archegonia are found in the same way, but upon special modi- 
fied branches. In the foliose Jungermanniaceae the origin of 
the archegonia is somew^hat different. Here they are formed 
upon short branches, where, after a small number of perichsetial 
leaves have been formed, the subsequent segments of the apical 



i6 MOSSES AND FERNS chap. 

cell develop archegonia at once, and finally the apical cell itself 
becomes the mother cell of the last-formed archegonium, and, 
of course, with this the growth in length of the branch ceases. 
With the exception of the Anthocerotes, where the arche- 
gonium mother cell does not project at all, it quickly assumes 
a papillate form and is divided by a transverse wall into a basal 
cell, and an outer one from which the archegonium itself 
develops. The divisions in this outer cell are remarkably 
uniform. Three vertical walls are first formed, intersecting so 
as to enclose a central cell (Fig. 2, G). In this central cell a 
transverse wall next cuts off a small, upper cell (cover cell) 
from a lower one. Subsequently the three (or in the 
Jungermanniacese usually but two) first- formed peripheral 
cells divide again vertically, and by transverse walls in all of 
the peripheral cells, and somewhat later in the central one also, 
the young archegonium is divided into two tiers, a lower one 
or venter, and an upper one, the neck (Fig. 2, F). The middle 
cell of the axial row, by a series of transverse walls, gives 
rise to the row of neck canal cells, and the lowermost cell 
divides into two an upper one, the ventral canal cell, and a 
larger lower one, the egg. 

The antheridium shows very much greater diversity in its 
structure, and equally great difference in its position. The 
origin in the thallose forms is usually the same as that of the 
archegonium, and indeed where the two grow mixed together, 
as in many species of Riccia, it is sometimes difficult to 
distinguish them in their earliest stages. Usually, however, 
the antheridia are borne together, either on special branches 
{Marchantia, species of Aneura), or they are produced in a 
special part of the ordinary thallus, which usually presents a 
papillate appearance (e.g., Fimhriaria) . In the foliose Junger- 
manniacese the antheridia are often borne singly in the axils 
of slightly modified leaves, but in no case does the apical cell 
of the shoot become transformed into an antheridium. The 
antheridium, like the archegonium, arises from a single super- 
ficial cell. The first division usually divides the primary cell 
into a stalk cell and the body of the antheridium. The first 
may remain very short and undergo but few divisions, or it 
may develop into a stalk of considerable length. The first 
division in the upper cell may be either transverse (Marchan- 
tiacese, Sphcorocarpus) or vertical (Jungermanniacese). 



II MUSCINEJE—HEPA TIC^— MARCH ANTI ALES 17 

Later, by a series of periclinal walls, a central group of cells is 
separated from an outer single layer of cells. The latter divide 
only a few times, and develop chlorophyll, which sometimes 
changes into a red or yellow pigment at maturity. The inner 
cells give rise to a very large number of sperm cells, which in 
most Hepatic?e are extremely small, and consequently not well 
adapted to studying the development of the spermatozoids. In 
a few forms, however, they are larger ; and in Pellia especially, 
where the sperm cells are relatively large, the development has 
been carefully studied by Guignard (i), Buchtien (i), and 
others of late years, as well as by many of the earlier observers, 
and a comparison with other Hepaticse shows great uniformity 
in regard to the origin and development of the spermatozoid. 
After the last division of the central cells the nuclei retain their 
flattened form, and thus the sperm cells or spermatids remain 
in pairs, an appearance very common in the ripe antheridium 
of most Liverw^orts. Just before the differentiation of the 
body of the spermatozoid begins, the nucleus has the appearance 
of an ordinary resting nucleus, but no nucleolus can be 
seen. The first change is an indentation in the edge of the 
discoid nucleus, and this deepens rapidly until the nucleus 
assumes a crescent form. One of the ends is somewhat sharper 
and more slender than the other, and this constitutes the 
anterior end. As the body of the spermatozoid grows in 
length it becomes more and more homogeneous, the separate 
chromosomes apparently fusing together as the body develops. 
The body of the spermatozoid increases in length until it forms 
a slender spiral band coiled in a single plane, lying parallel with 
the one in its sister cell. The full-grown spermatozoid in 
Pellia epiphylla has, according to Guignard ((i), p. 67) from 
three to four complete coils. Usually when the spermatozoid 
escapes, it has attached to the coil a small vesicle which swells 
up more or less by the absorption of water. This vesicle is 
the remains of the cytoplasm of the cell, and may, perhaps, 
contain also some of the central part of the nucleus. Gui- 
gnard ((i), p. 66) asserts that sometimes the cytoplasm is all 
used up during the growth of the spermatozoid, and that the 
free spermatozoid shows no trace of a vesicle. 

In the Ricciacese and in Spliccrocarpus new archegonia 
continue to form even after several have been fertilised, so that 

numerous sporogonia develop upon the same branch of the 
2 



i8 MOSSES AND FERNS chap. 

thallus; but in most Liverworts the fertilisation of an arche- 
gonium checks the further formation of archegonia in the same 
group, and only those that are near maturity at the time reach 
their full development ; and even if more than one archegonium 
of a group is fecundated, as a rule but one embryo comes to 
maturity. 

The Sporophyte 

Unquestionably the lowest type of sporogonium is found 
in Riccia (Fig. 6). Here the result of the first divisions in 
the embryo is a globular mass of cells, which a little later shows 
a single layer of peripheral cells and a central mass of spore 
mother cells, all of which produce spores in the usual way. 
The sporogonium remains covered by the venter of the arche- 
gonium until the spores are ripe, and never projects above the 
surface of the thallus. The spores only escape after the thallus 
(or at least that part of it containing the sporogonia) dies and 
sets them free as it decays. In the genus Sphcerocarpus (Fig. 
30), which may be taken to represent the next stage of develop- 
ment, we notice tw^o points in which it differs from Riccia. In 
the first place there is a basal portion (foot), which is simply an 
absorbent organ, and takes no part in the production of spores. 
Secondly, only a part of the archesporium develops perfect 
spores. A number of the spore mother cells remain undivided, 
and serve simply to nourish the growing spores. In the 
majority of the Hepaticge the sporogonium shows, besides the 
foot and the capsule, an intermediate portion, the stalk or seta, 
which remains short until the spores are ripe, when, by a rapid 
elongation of its cells, the capsule is forced through the calyptra 
and the spores are discharged outside. In these forms, too, 
some of the cells of the archesporium remain undivided, and 
very early are distinguished by their elongated shape from the 
young spore mother cells. These elongated cells later develop 
upon the inner surface of the cell wall peculiar spiral thickened 
bands, which are strongly hygroscopic. These peculiar fusi- 
form cells, the elaters, are found more or less developed in all 
the Hepaticse except the lowest ones. 

The dehiscence of the sporogonium is different in the 
different orders. In the Ricciacese and some Marchantiacese 
the ripe sporogonium opens irregularly; in a few cases (species 
of Fimbriaria) the top of the capsule comes off as a lid; ir 



II MUSCINE^—HEPA TICJE— MARCH ANT I ALES 19 

most Jungermanniales the wall of the capsule splits vertically 
into four valves. 

The spores are always of the tetrahedral type, i.e., the 
nucleus of the spore mother cell divides twice before there is 
any division of the cytoplasm, although this division may be 
indicated by ridges projecting into the cell cavity, and partially 
dividing it before any nuclear division takes place. The four 
nuclei are arranged at equal distances from each other near the 
periphery of the mother cell, and then between them are formed 
simultaneously cell walls dividing the globular mother cell into 
four equal cells having a nearly tetrahedral form. These 
tetrads of spores remain together until nearly full grown, or in 
a few cases until they are quite ripe. In the ripe spore two, 
sometimes three, distinct coats can be seen, the inner one 
(endospore, intine) of unchanged cellulose, the outer one 
(exospore, exine), strongly cutinized and usually having upon 
the outside characteristic thickenings, ridges, folds, spines, etc. 
Where these thickenings are formed from the outside they 
constitute the third coat (perinium, epispore). The exospore 
is especially well developed in species where the spores are 
exposed to great heat or dryness, and which do not germinate 
at once. In those species that are found in cooler and moister 
situations, especially where the spores germinate at once, the 
exospore is frequently thin. The nucleus of the ripe spore is 
usually small. The cytoplasm is filled with granules, mostly 
albuminous in nature, with some starch and generally a great 
deal of fatty oil that renders the contents of the fresh spore 
very turbid. Some forms, especially the foliose Junger- 
manniacese, have also numerous chloroplasts, but these are lack- 
ing usually in those forms that require a period of rest before 
germination. In Pellia and Conocephahis the first divisions in 
the germinating spore take place while the spores are still 
within the sporogonium. 

The germination of the spores begins usually by the forma- 
tion of a long tube (germ-tube, "Keimschlauch" of German 
authors), into which pass the granular contents of the spore. 
At the same time there may be formed a rhizoid growing in 
a direction opposite to that of the germinal tube, although quite 
as often the formation of the first rhizoid does not take place 
until a later period. If the spore does not contain chlorophyll 
before germination, it is developed at an early stage, before any 



20 • . MOSSES AND FERNS chap. 

cell-divisions occur. Often the formation of a germ-tube is 
suppressed and a cell surface or cell mass is formed at once, 
and all these forms may occur in the same species. The 
germination only takes place when the light is of sufficient 
intensity, and the amount of light is a very important factor 
in determining the form of the young plant. Thus if the light 
is deficient, the germ-tube becomes excessively long and slender, 
and divisions may be entirely suppressed. An excess of light 
tends to the development at once of a cell surface or cell mass. 
In the simpler thallose forms the first few divisions in the 
young plant establish the apical cell, and we cannot properly 
speak of the gametophore as arising secondarily from a 
protonema ; in other cases, however, the young plant does arise 
as an outgrowth or bud from a protonema, which only rarely 
has the branching filamentous character of the Moss protonema. 

Classification of the Hepaticae 

The Hepaticae are readily separated into the two following 
well-marked orders : 

Order I Marchantiales. 
Order II. Jungermanniales. 

The following diagnoses are taken, with some modifica- 
tions from SchifTner ((i), p. 5) : 

Order I. Marchantiales. 

Gametophyte always strictly thallose, composed of several 
distinct layers of tissue, the uppermost or chlorophyll-bearing 
cells usually containing large air-spaces. The dorsal epidermis 
usually provided with pores, ventral surface with scales ar- 
ranged in one or two longitudinal rows. Rhizoids of two 
kinds, those with smooth walls, and papillate ones; sexual 
organs, except in the lowest forms, united in groups which 
are often borne on special stalked receptacles. The first 
divisions of the embryo are arranged like the quadrants of a 
sphere. Sporogonium either with or without a stalk, and all 
the inner cells forming spores, or some of them producing 
elaters. No columella present. 



II MUSCINEyE—HEPA TIC^— MARCH ANTI ALES 21 

Fam. I. Ricciacccc 

Chlorophyll-bearing tissue with or without air-chambers, 
and, where these are present, they never contain a special assim- 
ilative tissue. Epidermal pores wanting or rudimentary. 
Sexual organs immersed in open cavities upon the dorsal 
surface. Sporogonium without foot or stalk, and remaining 
permanently within the venter of the archegonium. All the 
cells of the archesporium produce spores. 

Fam. 2. Corsiniacece. 

Air-chambers well developed; epidermis with distinct 
pores; sexual organs in distinct groups, but the receptacles 
always sessile ; sporogonium with a short stalk, producing 
besides the spores sterile cells, which may have the form of 
very simple elaters. 

Fam. 3. MarchantiacecB. 

Air-chambers usually highly developed, and the chambers 
often containing a loose filamentous assimilative tissue. Pores 
upon the dorsal surface always present (except in Diimortiera 
and Monoclea) and highly developed, ring-shaped or cylin- 
drical. Sexual organs always in groups, usually upon special 
long-stalked receptacles. Sporophyte stalked and when ripe 
breaking through the calyptra, opening by teeth or a circular 
cleft, more seldom by four or eight valves. The archesporium 
develops sterile cells, in the form of elaters, as w^ell as spores. 

The Marchantiales constitute a very natural order of 
plants, all of whose members agree very closely in their funda- 
mental structure. The separation of the Ricciacese as a group 
co-ordinate with the Jungermanniales and Marchantiales is not 
warranted, as more recent investigations, especially those of 
Leitgeb ( (7), vol. iv.) have shown that the two groups of the 
Marchantiacese and Ricciacese merge almost insensibly into each 
other. 

They are all of them strictly thallose forms, the thallus 
being unusually thick and fleshy, and range in size from a few 
millimetres in some of the smaller species of Riccia, to 10 to 20 
centimetres in some of the larger species of Diimortiera and 
Conocephahis. In most of them branching is prevailingly 



22 



MOSSES AND FERNS 



CHAP. 



dichotomous, and as this is rapidly repeated, it often causes the 
thallus to assume an orbicular outline. Some forms, however, 




1 






Fig. I. — Marchantiales. A, B, Male plants of Fimbriaria Californica. A, from above; 
B, from below; (^, antheridial receptacle; /, ventral lamellae, X4; C, Riccia glauca, 
X6; sp, sporogonia; D, Conocephalus conicus, X4; E, Targionia hypophylla, X2; 
^, antheridial branch. 

e.g., Targionia (Fig. i, E), may fork comparatively seldom, 
and the new branches are for the most part lateral. The thallus 



II MUSCINE^—HEPA TIC^— MARCH ANTI ALES 23 

is fastened to the substratum by rhizoids, which are unicellular 
and usually of two kinds, those with smooth walls and those 
with peculiar papillate thickenings or teeth that project inward 
(Fig. 12). The cells of the lower layers of tissue are usually 
nearly or quite destitute of chloroplasts, which, however, occur 
in large numbers in the so-called chlorophyll-bearing layer, just 
below the dorsal epidermis. This chlorophyll-bearing layer 
contains air-spaces in all forms except some species of 
Dumortiera and M on odea, and these spaces are either simple 
narrow canals, as in Riccia glmica, or they may be large cham^ 
bers separated by a single layer of cells from their neighbors. 
Such forms occur in most of the higher Marchantiaceae. 

The grow^th of the thallus is due to the division of a small 
group of cells occupying the bottom of the heart-shaped indent- 
ation in the forward part of the thallus. Sections parallel to 
the surface, cutting through this group, show a row of mar- 
ginal cells that appear very much alike, and it is impossible 
always to tell certainly whether or not there is a single definite 
initial cell. Such a single initial is unquestionably present in 
the earlier stages, and it is quite possible that it may persist, but 
owing to its small size and its close resemblance to the adjoin- 
ing cells, this cannot be positively asserted. In vertical sections 
the initial cell (or cells) appears nearly triangular, with the 
free outer wall somewhat convex. From this cell two sets of 
segments are cut off, the dorsal segments giving rise to the 
green tissue, and the lower segments producing the ventral 
lamellae and colourless lower layers of cells of the thallus. 

The plants multiply asexually either by the older parts of 
the thallus dying away and leaving the growing points isolated, 
or lateral branches, which are often produced in great numbers 
from the lower surface of the midrib, become detached and each 
branch forms a separate plant. The wxll-known gemmae of 
Marchantia and Lunularia are the most striking examples of 
special asexual reproductive bodies. 

The sexual organs are always derived from the dorsal 
segments of the apical cell, either of the ordinary branches or 
of special shoots. The archegonium is of the typical form, and 
the antheridium always shows a series of transverse divisions 
before any longitudinal walls are formed in it. 

While the gametophyte may reach a very considerable 
degree of specialisation, the sporophyte is relatively insignifi- 



24 MOSSES AND FERNS chap. 

cant even in the higher forms, and has the foot and stalk poorly 
developed. While the Marchantiales grow for the most part 
in moist situations, and some of them, e.g., Marchantia poly- 
morpha, are very quickly killed by drying, some species, e.g., 
Riccia trichocarpa, a common California species, grow by pref- 
erence in exposed rocky places exposed to the full force of the 
sun. This latter species as well as several others of the same 
region, e.g., Fimbriaria Calif ornica, Targionia hypophylla, do 
not die at the end of the rainy season, but become completely 
dried up, in which condition they remain dormant until the 
autumn rains begin, when they absorb water and begin to grow 
again at once. In these cases usually only the ends of the 
branches remain alive, so that each growing tip becomes the 
beginning of a new plant. 

The Ricciace^ 

As a type of the simplest of the Marchantiacese, we may 
take the genus Riccia, represented, according to Schiffner 
((i), p. 14), by 107 species, distributed over the whole earth. 
Most of them are small terrestrial plants forming rosettes upon 
clay soil or sometimes in drier and more exposed places. A 
few species, e.g., R. Huitans, are in their sterile condition sub- 
mersed aquatics, but only fruit when by the evaporation of the 
water they come in contact with the mud at the bottom. 

The dichotomously branched thallus shows a thickened 
midrib, which is traversed upon the dorsal surface by a longi- 
tudinal furrow which in front becomes very deep. At the 
bottom of this furrow, at the apex of the thallus, lies the grow- 
ing point. A vertical section through this shows a nearly 
triangular apical cell which lies much nearer the ventral than 
the dorsal surface (Fig. 2, x). From this are cut off succes- 
sively dorsal and ventral segments. Each segment next 
divides into an inner and an outer cell. From the outer cells 
of the dorsal segments the sexual organs arise, and from those 
of the ventral segments the overlapping lamellae upon the lower 
surface of the thallus, and also the rhizoids. The rapid 
division of the inner cells of the segments, especially those of 
the dorsal ones, causes the thallus to become rapidly thicker 
back of the apex. Sections made parallel to the surface of the 
thallus, and passing through the growing point (Fig. 3), show 



II 



MUSCINEAL— HEPATIC^— MARCH ANTI ALES 



25 



that the margin is occupied by a group of cells that look very 
much alike. Sometimes one of these cells is somewhat larger 
than the others, but more commonly it is impossible to decide 
with certainty that a single initial is present. From a com- 
parison of the two sections it is at once evident that the initial 
cells have nearly the form of the segment of a disc, and that in 
addition to the dorsal and ventral segments lateral ones are cut 
off as well. In the region just back of the apex the tissue of 




Fig. 2. — Riccia glauca. Development of the archegonium, XS^S- A, Vertical section 
through the growing point; x, apical cell; ar, young archegonium; //, ventral 
lamellae; B-F, successive stages in the development of the archegonium, seen in 
longitudinal section; G, cross-section of young archegonium (diagrammatic). 

the thallus is compact, but in the older parts a modification is 
observable both on the dorsal and ventral surfaces. In the 
former, a short distance from the growling point, the superficial 
cells project in a papillate manner above the surface. This 
causes little depressions or pits to be formed between the adja- 
cent cells (Fig. 3, C). The subsequent divisions in the papillae 
are all transverse, and this transforms each papillate surface cell 
into a row of cells which, as it elongates, causes the pits 
between it and the adjacent ones to become deep but narrow 
air-channels, so that in the older parts of the thallus the upper 
portion is composed of closely-set vertical rows of chlorophyll- 
bearing cells separated by narrow clefts opening at the surface. 



26 



MOSSES AND FERNS 



CHAP. 



In Riccia glauca, as well as other species, the uppermost cell of 
each row often enlarges very much, and with its fellows in the 
other rows constitutes the epidermis. According to Leitgeb's 
researches this epidermal cell is formed by the first division in 
the outer cell of the segment, and either undergoes no further 
division, or by dividing once by a transverse wall forms a two- 
layered epidermis ( R. BischoMi). On the ventral side the 
outer cells of the segments project in much the same way, but 




Fig. 3. — Riccia glauca. Horizontal sections of the growing point. A, B, X525; C, 
X about 260. C shows the dichotomy of the growing point; x, x' , the two new 
growing points; L, the lobe between them; ar, a young archegonium. 



they remain in close contact laterally with the neighboring cells, 
so that instead of forming isolated rows of cells, transverse 
plates or lamellae, occupying the median part of the lower sur- 
face of the thallus, are formed. These remain but one cell 
thick, and grow very rapidly, and bend up so as to completely 
protect the growing point. With the rapid widening of the 
thallus in the older parts these scales are torn asunder, and the 
two halves being forced apart constitute the two rows of ventral 
scales found in the older parts. Later these scales dry up and 



It MUSCINEM—HEPA TIC^—MARCHANTIALBS 27 

are. often scarcely to be detected except close to the growing 
point. 

In the case of Ricciocarpiis natans (Leitgeb (7), iv., p. 29) 
instead of a single scale being formed, each cell of the horizon- 
tal row, which ordinarily gives rise to a single scale, grows 
out independently, much as do the dorsal surface cells in the 
other species, and the result is a horizontal series of narrow 
scales, each one corresponding to a single cell of the original 
row. These later are displaced by the subsequent growth of 
the thallus, and their arrangement in transverse series can only 
be seen in the younger parts. The very rapid increase in length 
of the dorsal rows of cells as they recede from the growing 
point soon causes them to overarch the latter, which thus comes 
to lie in a deep groove ; indeed not infrequently the end cells of 
the rows on opposite sides of the groove actually meet, so that 
the groove becomes a closed tube. 

R. Unitans (Leitgeb (7), iv. p. 11) and R. crysfaUina differ 
in some respects from the other forms. In these, owing to a 
greater expansion of the tissues of the older parts of the thallus, 
the air-spaces are very much enlarged. In the former they are 
almost completely closed above, as the epidermal cells, by 
repeated vertical divisions, keep pace with the growth of the 
thallus and form a continuous epidermis, wath only a small 
central pore over each of the large air-chambers. In R. crys- 
tallina, however, there is no such secondary growth of the 
epidermal cells, and in consequence the cavities are completely 
open above, so that the surface of the thallus presents a series 
of wide depressions separated by thin lamellae. These tw^o 
species also show some difference as to the ventral scales. 
Those of R. Unitans are small and do not become separated into 
two, and in R. crystallina they are wanting entirely. 

Most of the Ricciacese multiply by special adventive shoots 
that arise from the ventral surface of the midrib. These 
become detached and form new individuals. According to 
Fellner ( i ) the rhizoids develop at the apex a young plant in a 
manner entirely similar to that by which the young plant arises 
from the germ tube of the germinating spore. 

By far the commonest method of branching in most species 
of Riccia is a true dichotomy. The first indication of this 
process is a widening of the growing point and a correspond- 



28 MOSSES AND FERNS chap. 

ing increase in the number of the marginal cells. The central 
cells of the marginal group now begin to grow more vigorously 
than the others and to project as a sort of lobe (Fig. 3, C, L), 
and this lobe divides the initial cells into two groups lying 
on either side of it. As soon as this is accomplished each 
new group of initial cells continues to grow in the same manner 
as the original group, and two new growing points are estab- 
lished, each of which develops a separate branch. The growth 
of the middle lobe is limited, and it remains sunk in the fork 
between the two new branches. 

The thallus is attached to the substratum by rhizoids of 
two kinds. The first are smooth-walled elongated cells, with 
colourless contents, the others much like those of the higher 
Marchantiacese. Their walls are undulating, and projecting 
inward are numerous more or less developed spike-like protu- 
berances. The rhizoids arise from large superficial cells of 
the ventral part of the midrib. They are readily distinguished 
from the adjacent cells by their much denser contents, even 
before they have begun to project. 

The arrangement of the tissues of the fully-developed 
thallus is best seen in vertical cross-sections. In R. glauca and 
allied forms four well-marked tissue zones can be readily 
recognized in such a section. The lowest consists of a few 
layers of colourless rather loose parenchyma, from which the 
rhizoids arise, and to which the ventral lamellae are attached. 
Above this a more compact, but not very clearly limited region, 
the midrib. The elongated form of the midrib cells, which 
contain abundant starch but no chlorophyll, is, of course, not 
evident in cross-section. Radiating from the midrib are 
closely-set rows of chlorophyll-bearing cells with the charac- 
teristic narrow air-spaces between. The median furrow is very 
conspicuous in such a section, and extends for about half the 
depth of the thallus. Terminating each row of green cells is 
the enlarged colourless epidermal cells, often extended into a 
beak-like appendage. In some species, e.g., R. trichocarpa, 
some of the surface cells grow out into stout thick-walled 
pointed hairs. 

The Sexual Organs 

In Riccia the sexual organs are formed in acropetal suc- 
cession from the younger segments of the initial cells, and 



II MUSCINE^—HEPA TIC^— MARCH ANTI ALES 29 

continue to form for a long time, so that all stages may be met 
with upon the same thallus. While both antheridia and arche- 
gonia may be found together, in the two species R. glauca and 
R. trichocarpa, mainly studied by myself, I found that as a rule 
several of one sort or the other would be formed in succession, 
and that not infrequently antheridia were quite wanting upon 
plants that had borne numerous archegonia. Both archegonia 
and antheridia arise from single superficial cells of the younger 
dorsal segments of the initial cells. In their earliest stages 
they are much alike, the mother cell of the antheridium being, 
however, usually somewhat larger than that of the arche- 
gonium. The cell enlarges and projects as a papilla above the 
surface, when it is divided by a transverse wall into an outer 
cell and an inner one. The latter divides but a few times and 
forms the short stalk ; the outer cell, which has dense granular 
contents, develops into the archegonium or antheridium as the 
case may be. In the former case the divisions follow the 
order already indicated for the typical Liverwort archegonium. 
In the outer cell, which continues to enlarge rapidly, a nearly 
vertical wall is formed (Fig. 2, C), which divides the cell into 
two very unequal parts. This wall is curved and strikes the 
periphery of the mother cell at about opposite points (Fig. 2, 
G, i). A second wall of similar form is next formed in the 
larger cell (G, 2), one end of which intersects the first wall, 
and finally a third wall (3) intersecting both of the others is 
formed. The young archegonium seen in vertical section at 
this stage (Fig. 2, D) shows a large central cell bounded by 
two smaller lateral ones ; in cross-section the central one 
appears triangular. Each of the four cells of which the arche- 
gonium rudiment is now composed divides into two. The 
outer ones each divide by radial walls into equal parts, and the 
central one divides into an upper smaller cell (cover cell) and 
a lower larger one (Fig. 3, E). The next divisions are hori- 
zontal and divide the young archegonium into two tiers of cells. 
The lower one forms the venter, and the upper one the neck, 
and next the cover cell divides into four nearly equal cells by 
intersecting vertical walls. The archegonium at this stage 
(Fig. 2, F) is somewhat pear-shaped, being smaller at the 
bottom than at the top, and the basal cell is still undivided. 
It now rapidly increases in length by the transverse division 
and growth of all its cells, and there is at the same time a 



30 



MOSSES AND FERNS 



CHAP. 



marked increase in diameter in the venter, which finally becomes 
almost globular (Fig. 4). The axial cell of the neck, the neck 
canal cell, divides, according to Janczewski (i), always into 
four in R. BischofHi, and the same seems to be true for R. fricho- 
carpa (Fig. 4, A), and probably is the same in other species. 
The number of divisions in the outer neck cells is various, but 
is most active in the lower part, but in the central cell of the 
venter there is always but a single transverse division which 





Fig. 4. — ^A, Archegonium of Riccia trichocarpa, showing the ventral canal cell (f), 
XS25; B, ripe archegonium of R. glauca, longitudinal section, X260. 



separates the ventral canal cell from the ^gg. The four 
primary cover cells enlarge a good deal as the archegonium 
approaches maturity, and divide by radial walls usually once, 
so that the complete number is normally eight — Janczewski 
gives ten in R. BischoMi. The basal cell finally divides into a 
single lower cell which remains undivided, completely sunk in 
the thallus, and an upper cell which divides into a single layer 
of cells forming part of the venter, and continuous with the 
other peripheral cells. The mature archegonium (Fig. 4) 



n MUSCINE^— HEPATIC^— MARCHANTIALES 31 

has the form of a long-necked flask with a much enlarged base. 
The canal cells are completely indistinguishable, their walls 
having become absorbed and the contents run together into a 
granular mass. The nuclei of the neck-canal cells are small 
and not readily recognisable after the breaking down of the 
cell walls, but from analogy with the higher forms it is not 
likely that they completely disappear in the ripe archegonium. 
The cytoplasm of the central cell contracts to form the naked 
globular Qgg. The cytoplasm is filled with granules, and the 
nucleus, which is of moderate size, shows a distinct nucleolus, 
but very little chromatin. A special receptive spot was not 
certainly to be seen. 

Almost coincident with the first cell division in the arche- 
gonium rudiment there is a rapid growth of the cells imme- 
diately surrounding it. These grow up as a sort of ring or 
ridge about the archegonium, which is thus gradually immersed 
in a cup-shaped cavity, and the growth of the cells about this 
keeps pace with the increase in length of the archegonium, so 
that even when fully grown only the very extremity of the 
neck projects above the level of the thallus. The whole process 
is undoubtedly but a modification of the ordinary growth of 
the dorsal part of the thallus, and the space about the arche- 
gonium is the direct equivalent of the ordinary air-spaces. 

The first division in the primary antheridial cell is the 
same as in the archegonium, but the later divisions differ much 
and do not show such absolute uniformity. The first division 
wall in the upper cell (Fig. 5, B) is always transverse, and 
this is followed by a second similar wall, but the subsequent 
divisions show considerable variation even in the same species. 
After a varying number of transverse walls have been formed, 
in most cases the next divisions, which are formed only in the 
middle segments, are vertical, and divide the segments into 
quadrants of a circle when seen in transverse section. Occa- 
sionally a case is met with where the division walls are inclined 
alternately right and left, and the divisions strongly recall 
those of the typical Moss antheridium (Fig. 5, D). 

The separation of the sperm cells is brought about by a 
series of periclinal walls in a number of the middle segments, 
by which four central cells in each segment (Fig. 5, G) are 
separated from as many peripheral cells. These central cells 



22 



MOSSES AND FERNS 



CHAP. 



have, as usual in such cases, decidedly denser contents than the 
peripheral ones. 

The lower one or two segments and the terminal ones do 
not take part in the formation of sperm cells, but simply form 

c 

A. 









Ql 





(!) 



Fig. s. — A-F, Development of the antheridium of R. glauca, seen in longitudinal 
section; G, cross-section of a young antheridium of the same; H, antheridium of 
R. trichocarpa; I, sperm cells of R. glauca. Figs. E, F, X150; I, X600, the 
others X300. 



part of the wall of the antheridium. The central cells now 
divide with great rapidity, the division walls being formed 
nearly at right angles to each other, so that the central part of 
the antheridium becomes filled with a very large number of 
nearly cubical cells. The divisions are formed with such 
regularity that the boundaries of the original central cells 
remain very clearly marked until the antheridium is nearly 
mature. The basal cell of the antheridium rudiment in R. 
glauca divides once by a horizontal wall (Fig. 5, B, D) and 
forms the short stalk of the antheridium, which, however, is 
almost completely sunk in the thallus. Between this stalk 
and the central group of cells there are usually two layers of 
cells, so that the wall of the antheridium is double at the base, 
while it has but a single layer of cells in the other parts. The 



II MUSCINEM— HEPATIC^— MARCH ANTI ALES 33 

uppermost cells are often, althoug-h not always, extended into 
a beak. The spermatozoids do not seem to differ either in 
their method of development or structure from those of other 
Hepatic?e, but their excessively small size makes it extremely 
difficult to follow through the details of their development. 
When ripe the wall cells are much compressed, but are always 
to be distinguished. 

Like the archegonia, the antheridia are sunk separately in 
deep cavities, which are formed in exactly the same way. 
Unlike the archegonia, however, the antheridium does not 
nearly reach to the top of the cavity, whose upper walls are in 
many species very much extended into a tubular neck, which 
projects above the general level of the thallus, and through 
which the spermatozoids are discharged. 

The Sporophyte. 

After fertilisation is effected the tgg develops at once a 
cell-membrane and enlarges until it completely fills the cavity 
of the venter. The first division w^all is more or less inclined 
to the axis of the archegonium, but approaches usually the 
horizontal. The lower of the tw^o cells thus formed divides 
first by a wall at right angles to the first formed, but this is 
followed in the upper half of the embryo by a similar division, 
so that the embryo is divided into nearly equal quadrants. In 
each of the quadrants a wall meeting both of the others at 
right angles next appears (Fig. 6, C, III), and the embryo at 
this stage consists of eight nearly equal cells. The next walls 
are not exactly alike, but the commonest form is a curved wall 
(Fig. 6, C), striking two of the others, usually walls II and III, 
and intersecting the surface of the embryo. This wall divides 
the octants into two cells, which appear respectively triangular 
and quadrilateral in section. By the next division the arche- 
sporium is separated from the wall of the sporogonium. These 
W2.\\s, are periclinal, and by them a single layer of outer cells is 
separated from the central mass of cells which constitutes the 
archesporium (Fig. 6, B, D). 

At first the cells of the embryo are much alike, but as it 

grows the inner cells increase in size and their contents become 

densely granular, while the outer cells grow only in breadth, 

and not at all in depth, assuming more and more a tabular 
3 



34 



MOSSES AND FERNS 



CHAP. 



form, and for the most part undergo divisions only in a radial 
direction so that the walls remain but one cell thick in most 
places. As the sporogonium increases in diameter the central 
cells begin to separate and round off. Their walls become 
partially mucilaginous, and in microtome sections stain 
strongly with Bismarck-brown or other reagents that stain 
mucilaginous membranes. With this disintegration of the 
division walls the cells separate more and more until they lie 
free within the cavity of the sporogonium. Each of these 
spore mother cells is a large globular cell with thin membrane 




m. 





Fig. 6. — ^A, B, Young embryos of R. glauca in longitudinal section, showing the 
venter of the archegonium, X260; C, transverse section of a similar embryo, 
X260; D, longitudinal section of the archegonium and enclosed embryo of R. 
trichocarpa at a later stage, X220; m, the sterile cells of the sporogonium. 



and densely granular contents. The nucleus is not so large as 
is usually the case in cells of similar character, and, except the 
nucleolus, stains but slightly with the ordinary nuclear stains. 
In the fresh state these spore mother cells are absolutely opaque, 
owing to the great amount of granular matter, largely drops of 
oil, that they contain. In embedding these in paraffine, 
however, the oil is dissolved and removed, and microtome 
sections show the fine granules of the cytoplasm arranged in a 
net-like pattern, the spaces between probably being occupied 
by oil in the living cells. 



II 



MUSCINE^— HEPATIC^— MARCH ANTI ALES 



35 



Fig. 7, A shows the nucleus of the mother cell under- 
going the first division. The small size of the nuclei, and the 
small amount of chromation in them, make the study of the 
details of the nuclear division difficult here, and as there was 
nothing to indicate any special peculiarities these were not 
followed out. After the first nuclear division the daughter 
nuclei divide again, after which the four nuclei arrange them- 




c. 





Fig. 7.—Riccia trichocarpa. A, Section of a spore mother cell undergoing its first 
division, X6oo; B, section of young spore tetrad, X300; C, section of ripe spore, 
X300; D, surface view of the exospore of a similar stage, X300. 



selves at equal distances from each other, the division w^alls 
form simultaneously between them, dividing the spore mother 
cell into the four tetrahedral spores. A section through such 
a young spore-tetrad is shown in Fig. 7, B, where one of the 
cells is somewhat shrunken in the processof embedding. The 
cell walls at this stage are very delicate and of unchanged 
cellulose ; but as they grow older the wall soon shows a separa- 
tion into endospore and exospore. The latter in R. tricho- 
carpa, which was especially studied, is very thick, at first 
yellowish in colour, but deepening until when ripe it is black. 
Sections parallel to the surface show in this species what 
appear to be regular rounded pits, but vertical sections of the 
spore-coat show that this appearance is due to a peculiar fold- 



36 MOSSES AND FERNS chap. 

ing of the exospore, which also shows a distinct striation, the 
outer layer being much thicker and denser than the inner ones. 
The nucleus of the ripe spore is remarkably small, and it is 
evident that the dense contents of the ripe spore are largely oil 
or some similar soluble substance, as in microtome sections 
there is very little granular matter visible. 

At the same time that the first division wall forms in the 
embryo, the outer cells of the venter begin to divide by 
periclinal walls, so that the single layer of cells in the wall of 
the unfertilised archegonium becomes changed into two, and 
the basal portion becomes still thicker; the neck takes no part 
in this later growth. The cells of the venter develop a great 
deal of chlorophyll, which is quite absent from the sporogonium 
itself, and before the spores are ripe the inner layer of cells of 
the calyptra (venter) becomes almost entirely absorbed, so that 
only traces of these cells are visible when the spores are ripe. 
The wall of the sporogonium also disappears almost completely 
as the latter matures, but usually in microtom.e sections traces 
of this can be made out in the ripe capsule, although the cells 
are very much compressed and partially disorganised. The 
contents of these cells, as well as the inner calyptra cells, no 
doubt are used up to supply the growing spores with nourish- 
ment. Thus, when ripe, the spores practically lie free in the 
cavity surrounded only by the outer layer of calyptra cells. 
The neck of the archegonium persists and is made conspicuous 
by the dark brown colour of the inner walls of the cells. 

Hitherto the germination of the Ricciacese was only known 
in R. glauca ( Fellner ( i ) ) . The account here given is based 
upon observations made upon R. trichocarpa — a very common 
Californian species. It fruits in winter and early spring, and 
the spores remain dormant during the dry summer months. 
If the spores are sown in the autumn they germinate within a 
few days by bursting the massive black exospore, through 
which the colourless endospore enclosing the spore contents 
projects in the form of a blunt papilla. This rapidly grows 
out into a long club-shaped filament (Fig. 8, A), much less in 
diameter than the spore, and into this the spore contents pass. 
These now contain albuminous granules and great numbers of 
oil-globules, and some chlorophyll bodies, which at first are 
small and not very numerous. They, however, increase rapidly 
in size, and divide also, so that before the first cell division 



II 



MUSCINEAi— HEPATIC^— MARCH ANTI ALES 



37 



takes place the chloroplasts are abundant and conspicuous. 
The formation of the first rhizoid does not take place usually 
until a number of divisions have been formed in the young 
thallus. The first rhizoid (Fig. 9, r) arises at the base of the 
germinal tube, and is almost free from granular contents. It, 
usually at least, is separated by a septum from the germ-tube. 
The first wall in the latter is usually transverse, although in 
exceptional cases it is oblique (Fig 8, C), and this is followed 
by a second one parallel to the first (Fig. 8, C). In each of 
these cells a vertical wall is formed, and then a second at right 
angles to this, so that the nearly globular mass of cells at the 




Fig. 8. — Riccia trichocarpa. Germination of the spores, X190. In E the figure at 
the left represents a surface view, the one at the right an optical section; K, 
germinal tube. 



end of the germ-tube is composed of eight nearly equal cells or 
octants. As these divisions proceed the oil drops which are so 
abundant in the undivided germ-tube disappear almost com- 
pletely, and are doubtless used up by the growing cells. 

According to Leitgeb's view, and that of other authors, the 
eight-celled body at the end of the germ-tube is a sort of pro- 
tonema, from which the gametophore arises as a lateral out- 
growth. I have seen nothing in the species under consideration 
which supports such a view. Here the axis of growth is con- 
tinuous with that of the germ-tube, and in some cases at least, 



38 



MOSSES AND FERNS 



CHAP. 



and probably always, a single apical cell is developed at the 
apex at a very early stage. Probably this initial ^ell is one of 
the four terminal octant cells resulting from the first divisions. 
This cell sometimes has but two sets of segments cut off from 
it at first, alternately right and left, but whether this form is 
constant in the young plant I cannot now say. 




Fig. g.—Riccia trichocarpa. Later stages of germination. A, from below, X260; 
B, optical section of A, showing apical cell x, XS2o; C, X85; r, rhizoids. Inter- 
cellular spaces have begun to develop. 



The four lower quadrants also divide, at first only by 
transverse walls, and these cells lengthening give rise to a 
cylindrical body composed of four rows of cells, terminated by 
the more actively dividing group of cells at the summit. The 
single apical cell is soon replaced by the group of initials found 
in the full-grown gametophyte, and the method of growth from 



II MUSCINE^—HEPA TICAL— MARCH ANT I ALES 39 

now on is essentially the same. The growth of the cells in the 
forward part of the dorsal surface of the young thallus is more 
active than that of the ventral side, so that they project over 
the growing point (Fig. 9), and as the outer cells of the lateral 
segments of the apical cell (or cells) also increase rapidly in 
size as they recede from the growing point, the forward margin 
of the thallus, seen from below, is deeply indented, and the 
forward part of the thallus is thus occupied by a deep cavity, at 
the bottom of which, toward the ventral side, lies the growing 
point. This cavity is the beginning of the groove or furrow 
found in the older thallus. 

At first the cells of the young thallus are without inter- 
cellular spaces, but at an early period (Fig. 9, C) the outer cells 
of the young segments separate and form the beginnings of the 
characteristic air-spaces. In R. trichocarpa some of the dorsal 
cells about the same time form short pointed papillae, the first 
indication of the pointed hairs characteristic of this species. 
As the plant grows, new rhizoids are formed by the growing 
out of ventral cells into papillae, which are cut ofif by a partition 
from the mother cell. These first-formed rhizoids are always 
smooth-walled, and it is only at a much later stage that the 
other form develops, as well as the ventral lamellae, which are 
quite absent from the young plant. 

Classification of the Ricciace^ 

Besides the genus Riccia, which includes all but three species 
of the family, there are two other genera, each represented by 
a single species, which undoubtedly belong here. Of these 
Ricciocarpus natans is of almost world-w^ide distribution. It 
is a floating form, like Riccia Huitans. Leitgeb ( (7), vol. iv.) 
has made a very careful study of the structure and development 
of the thallus, w^hich differs a good deal from that of Riccia, in 
which genus this plant was formerly placed. The apical 
growth is essentially the same, and the differentiation of the 
tissues begins in the same way, but the chlorophyll-bearing 
tissue is extraordinarily developed. The air-spaces are formed 
in the same way as in Riccia, but they become very deep, and 
at an early stage, while still very narrow, are divided by cel- 
lular diaphragms into several overlying chambers, which, nar- 
row at first, later become very wide, so that the dorsal part of 



40 



MOSSES AND FERNS 



CHAP. 



the thallus is composed of a series of large polyhedral air- 
chambers arranged in several layers, and separated by walls 
but one cell thick. The upper chambers communicate with 
the outside by pores, quite like those of the Marchantiaceae. 
The ventral tissue and midrib are rudimentary, and the very 
long pendent ventral lamellae are produced separately in trans- 
verse rows, which, however, become displaced by the later 
growth of the thallus, so that their original arrangement can 
no longer be made out. Oil bodies like those found in the 
Marchantiaceae occur. The terrestrial form, which grows on 
the margins of ponds, etc., where the floating form is found, 
is much more richly branched and more vigorous than the 
floating form (Fig. lo). The ventral scales become shorter, 

and numerous wide but unthick- 
ened rhizoids are formed, which 
are almost completely lacking in 
the floating form. The structure 
of the reproductive organs and 
sporogonium are essentially the 
same as in Riccia. 

Garber (i), who has recently 
studied the development of Riccio- 
carpus, finds that it is not dioecious, 
as has been frequently asserted, 

Fig. .o.-Ricciocarpus natans. A, but rather proteraudrous— that is, 
Floating form; B, terrestrial numcrous anther idia are formed, 
form, X2. ^^^ some time before the first arch- 

egonia develop. Occasionally no archegonia are formed. 

While the settling of the plant upon the mud is not a neces- 
sary condition for the development of the reproductive organs, 
as has been asserted by Leitgeb, still none are formed as a rule 
upon plants growing in permanent ponds, while those growing 
in temporary ponds regularly develop abundant reproductive 
organs. In permanent bodies of water, vegetative multipli- 
cation may be very rapid, and it has been found that after these 
are frozen over, a certain number of the plants survive, some- 
times sinking to the bottom, and resuming growth again in 
the spring. 

The third genus, Tesselina (Oxymifra), represented by the 
single species, T. pyramidata, is much less widely distributed, 
belonging mainly to Southern Europe, but also found in Para- 




11 MUSCINEJE— HEPATIC JE— MARCH ANTI ALES 41 

guay. This interesting form has also been carefully examined 
by Leitgeb ((7), iv., p. 34), who calls attention to its inter- 
mediate position between the RicciacCcC and the Marchantiaceae. 
The thallus has all the characters of the latter : air-chambers 
opening by regular pores, usually surrounded by six guard- 
cells ; two rows of ventral scales, independent from the begin- 
ning; and the sexual organs united into groups upon special 
parts of the thallus. The sporogonium, how^ever, is entirely 
like that of Riccia, so that it may properly be placed in the same 
family. The plants are dicecious and strictly terrestrial. 

A third genus, Croiiisia, represented also by a single species, 
C paradoxa, is placed provisionally with the RicciacCcC by 
Schififner ((i), p. 15), but the structure and development have 
not been investigated with sufficient completeness to make this 
certain. It has been found only in Brazil. Schiffner says of 
this form : "It belongs perhaps to the Corsinieae, and forms 
a direct transition from the Ricciacese to that family." 

The Corsiniace^ {Schiffner (i), p. 26). 

The family Corsiniaceae comprises but two genera, Corsinia 
and Funicitlaria (Boschia). Each genus contains but a single 
known species. Structurally they are intermediate in character 
between the Ricciaceae and Marchantiaceae. Corsinia differs 
from all the higher Marchantiaceae in the character of the ven- 
tral scales, which are formed in more than two rows, like those 
of Ricciocarpus. Boschia, the other genus, has two rows of 
scales of the ordinary form. The archegonia are borne in a 
group in a depression upon the dorsal surface of the thallus, but 
are not formed upon a special receptacle, although after fertili- 
sation the cells at the bottom of the cavity multiply actively and 
form a small prominence upon wdiich the young sporogonia are 
raised, and this may perhaps be the first indication of the arche- 
gonial receptacle in the other forms. 

The sporophyte resembles that of the Marchantiaceae, but 
the sterile cells in Corsinia do not develop into true elaters, and 
in both genera the foot is less developed than in the true Mar- 
chantiaceae. 

Marchantiace^. 

Comparing the Marchantiaceae wnth the Ricciaceae, the close 
similarity in the structure and development of the thallus is at 



42 MOSSES AND FERNS chap. 

once apparent, but the former are more highly developed in all 
respects. The development of definite air-chambers in the 
green tissue, and a continuous epidermis with the characteristic 
pores, is common to all of them with the exception of the 
peculiar genera Dumorfiera and Monoclea, where the develop- 
ment of the air-chambers is partially or completely suppressed. 
The genera Ricciocarpiis and Tessalina on the one hand, and 
Corsinia and Boschia on the other, connect perfectly Riccia 
with the Marchantiacese as regards the structure of air-spaces 
and epidermis, as they do in other respects. The epidermal 
pores in the Marchantiacese are sometimes simple pores sur- 
rounded by more or less symmetrically arranged guard cells 
(Fig. 1 1, D), or they are, especially upon the female receptacles, 
of a most peculiar cylindrical form, which arises by a series of 
transverse walls in the primary guard cells (Fig. ii, C). 
There is a good deal of difference in the character of the air- 
chambers in different genera. In Rehoiilia and Fimhriaria, 
for instance, they resemble a good deal those of Ricciocarpiis, 
a more or less complete division of the primary chambers being 
produced by the formation of diaphragms or laminae, which 
give the green tissue an irregular honey-combed appearance, 
and in these forms there is not a sharp separation of the 
green tissue from the ventral colourless tissue. In other 
genera, Marchantia, Targionia (Fig. i8), Conocephalus, the 
dorsal part of the thallus is occupied by a single layer of very 
definite air-chambers, each opening at the surface by a single 
central pore. Seen from the surface the boundaries of these 
spaces form a definite network which in Conocephalus (Fig. i, 
D) is especially conspicuous. The bottom of these chambers is 
sharply defined by the colourless cells that lie below, and the 
space within the chamber is filled by a mass of short, branching, 
conferva-like filaments, which in the centre of the chamber have 
free terminal cells, but toward the sides are attached to the 
epidermal cells and are more or less confluent with the adjacent 
filaments. 

As in Riccia rhizoids of two kinds are present, but the 
thickenings to the tuberculate rhizoids (Fig. 12) are much 
more pronounced, and these are not infrequently branched, and 
may extend nearly across the cavity of the hair. The ventral 
scales are not produced by the splitting of a single lamella, as 
in Riccia, but are separate from the first and usually arranged 



II 



MUSCINE^— HEPATIC^— MARCH ANTI ALES 



43 



in two rows. Leitgeb ((7), iv., p. 17), recognises two types 
of these organs. In their earHest stages they are ahke, and 
both arise from papih^e close to the growing point. In both 
cases this papilla is cut off from a basal cell, but in the first 
type {Saiiteria, Targionia, Dumortiera) it remains terminal, 
usually forming the tip of a leaf-like terminal appendage of 
the scale. In the second type, represented by most of the 
other genera, this originally terminal papilla is forced to one 
side by the development of a lateral appendage to the scale, 
which, arising at first from a single cell, rapidly increases in 

A. 



CDSSI^ 




Fig. II. — Fimbriaria Californica. Development of the pores upon the archegonial 
receptacle, X260. A, B, C, in longitudinal section; D, view from above. 



size, and forms the overlapping dark purple marginal part of 
the scale so conspicuous in many species. 

In different parts of the thallus are found large mucilage 
cells, which are usually isolated ; or in Conocephalus, according 
to Goebel's (i) investigations, and those of Cavers (6), they 
may form rows of cells which become confluent so as to form 
mucilage ducts. In the earlier stages these cells have walls 
not differing from those of the adjacent cells, but as they grow 
older the whole cell wall is dissolved, and the space occupied 
by the row of young cells becomes an elongated cavity filled 
with apparently structureless mucilage. These cells are recog- 
nisable at an early period, as their contents are much denser 
and more finely granular than those of the adjacent cells. 



44 



MOSSES AND FERNS 



CHAP. 




©c 



Small cells, each containing a peculiar oil body, are found 
abundantly in most species, both in the body of the thallus 
and in the ventral scales. The structure and development of 
these curious bodies, which are found also in many other 
Hepaticse, have been carefully studied by Pfeffer (2). The 
oil body has a round or oval form usually, and in the Mar- 
chantiese usually is found in a special cell which it nearly fills. 
It is brown or yellowish in colour, and has a turbid granular 
appearance. The extremely careful and exhaustive study of 
these bodies by Pfeffer has shown that the oil exists in the 
form of an emulsion in water, and that in addition to the oil 
and water more or less albuminous matter is pres- 
ent, and tannic acid. The latter is especially 
abundant in the oil bodies of Luniilaria, less so in 
Marchantia and Preissia ( Cavers ( 6) ; Kiister ( i ) ) . 
The thallus of the Marchantiacese is made up al- 
most entirely of parenchyma, but Goebel (3) 
states that in Preissia comniutata there are elon- 
gated sclerenchyma-like cells in the midrib. The 
walls of the large colourless cells of the lower lay- 
ers of the thallus are often marked with reticulate 
thickenings, which are especially conspicuous in 
Marchantia. 

Most of the Marchantiacese have no special non- 
sexual reproductive organs, but in the genera 
chantia poly- MaTchantia and Lunularia special gemmae are pro- 
mo r p /t a . (j^jced in enormous numbers; and in the latter 
tubercuiate form, w^hlch is extrcmcly common in greenhouses, 
rhizoid , ^j^g plant multiplies only by gemmae, as the plants 
are apparently all female. These gemmae, as is 
well known, are produced in special receptacles upon the dorsal 
side of the thallus. The receptacles are cup-shaped in Mar- 
chantia, and crescent-shaped in Lunularia, where the forward 
part of the margin of the cup is absent. These cups are appar- 
ently specially developed air-chambers, which, closed at first, 
except for the central pore, finally become completely open. 
The edge of the fully-developed receptacle is fringed. The 
gemmae arise from the bottom of the receptacle as papillate 
hairs, and their development is the same in the other two genera 
where they occur. Fig. 13 shows their development in M, 
polymorpha. 



II 



MUSCINE^— HEPATIC AL— MARCH ANTI ALES 



45 



One of the surface cells of the bottom of the receptacle 
projects as a papilla above the surface, and is cut off by a 
transverse wall from the cell below. The outer cell next 
divides again by a transverse wall into a lower cell, which 
develops no further, and a terminal cell from which the gemma 
is formed. This terminal cell first divides into two equal cells 
by a cross-wall (Fig. 13, B), and in each of these cells a similar 
wall arises, so that the young gemma consists of four nearly 

A. 





Fig. 13. — Marchantia polymorpha. A, Plant with gemma cups {k, k), X2; B-F, 
development of the gemmae, X525; G, an older gemma, X260; v, v', the two 
growing points. 

equal superimposed cells (Fig. 13, D). The wall III in Fig. 
13, D, arises a little later than wall II, and is always more or 
less decidedly concave upward. Each of the four primary 
cells of the gemma is divided into two by a central vertical wall, 
and this is followed by periclinal walls in each of the resulting 
cells. At first the gemma is but one cell in thickness, but 
later walls are formed in the central cells parallel to the sur- 
face, so that it becomes lenticular. As it grows older there 



46 MOSSES AND FERNS chap. 

is established on opposite sides (Fig. 13, G, v, v') the grow- 
ing points, which soon begin to develop in the manner found in 
the older thallus, and come to lie in a depression, so that the 
older gemmae are fiddle-shaped. The gemma stands vertically, 
and there is no distinction of dorsal and ventral surfaces. The 
cells contain chlorophyll, except here and there the cells with 
oil bodies, and an occasional large colourless superficial cell. 
Among them are small club-shaped hairs, wdiich secrete a 
mucilage that swells up when wet, and finally tears away the 
gemmae from their single-celled pedicels. 

The further development of the gemmae depends upon their 
position as to the light. Whichever side happens to fall down- 
ward becomes the ventral surface of the young plant, and the 
colourless cells upon this surface grow out into the first rhi- 
zoids. The two growing points persist, and the young plant 
has two branches from the first, growing in exactly opposite 
directions. As soon as it becomes fastened to the ground the 
dorsiventrality is established, and upon the dorsal surface the 
special green lacunar tissue and the epidermis with its charac- 
teristic pores are soon developed, while the ventral tissue loses 
its chlorophyll, and soon assumes all the characters found in 
the mature thallus. 

The branching of the thallus is in most cases dichotomous, 
as in Riccia, but occasionally, as in Targionia (Fig. i, E), the 
growth is largely due to the formation of lateral adventitious 
branches produced from the ventral surface. 

In structure and development the sexual organs correspond 
closely to those of the Ricciaceae, but they are always formed 
in more or less distinct groups or "inflorescences." As might 
be expected, this is least marked in the lower forms, especially 
the Corsinieas (Leitgeb (7), vol. iv.), where the main distinc- 
tion between them and the lower Ricciaceae is that in Corsinia 
the formation of sexual organs is confined to a special region, 
and that the archegonia do not have an individual envelope as 
in Riccia, but the whole group of archegonia is sunk in a com- 
mon cavity, which is of exactly the same nature as that in 
which each archegonium is placed in the latter. In most of 
the Marchantieae, however, both antheridia and archegonia 
are borne in special receptacles, which in the case of the latter 
are for the most part specially modified branches or systems of 
branches, raised at maturity upon long stalks (Fig. 21). The 



II MUSCINE^—HEPA TICAl—MARCHANTIALES 47 

antheridial receptacles are sometimes stalked, but inore com- 
monly are sessile, and often differ but little from those of the 
higher Ricciacese. 

The sporogonium shows an advance upon that of the 
Ricciacese by the development of a lower sterile portion, or foot, 
in addition to the spore-bearing portion or capsule, and in the 
latter there are always sterile cells, which in all but the lowest 
Corsinieae have the form of elaters. At maturity, also, the ripe 
capsule breaks through the calyptra, except in the Corsinieae, 
w^here, too, the sterile cells do not develop into elaters, but 
seem to serve simply as nourishing cells for the growing 
spores. The stalk of the capsule is usually short compared 
with that of most Jungermanniacese, and the wall of the capsule 
remains intact until the spores are ripe. 

The spores vary much in size, and in the development of 
the outer w^all. In Marchantia polymorpha and other species 
where the spores germinate promptly, the ripe spore contains 
chlorophyll, and the exospore is thin and slightly developed. 
In such cases there is no distinct rupture of the exospore, but 
the whole spore elongates directly into the germ-tube. In 
Conocephalus, where the spores are very large, the first divi- 
sions occur in the spores before they are scattered. In species 
where the spores do not germinate at once the process is much 
like that of Riccia, and the thick exospore is ruptured and 
remains attached to the base of the germ-tube. 

The apical growth of the Marchantiese is very much like 
that of Riccia. In Fimhriaria Calif ornica (Fig. 14) the apical 
cells seen in vertical section show the same form as those of 
Riccia, and the succession of dorsal and ventral segments is 
the same; but here the development of the ventral segments 
is much greater, and there is not the formation of the median 
ventral lamellae as in Riccia, but the two rows of ventral scales 
arise independently on either side of the midrib, very near the 
growing point, and closely overlap and completely protect the 
apex. The formation of the lacunae in the dorsal part of the 
thallus begins earlier than in Riccia, and corresponds very 
closely to what obtains in Ricciocarpiis. The pits are at first 
very narrow, but widen rapidly as they recede from the apex. 
In the epidermal cells surrounding the opening of the cavity, 
there are rapid divisions, so that the opening remains small 
and forms the simple pore found in this species. As in Riccio- 



48 



MOSSES AND FERNS 



CHAP. 



carpus, the original air-chambers become divided by the devel- 
opment of partial diaphragms into secondary chambers, which 
are not, however, arranged in any regular order, and communi- 
cate more or less with one another. 

In Targionia (Figs. i8, 19), where the archegonia are 
borne upon the ordinary shoots, the growth of the dorsal seg- 
ments is so much greater than that of the ventral ones that the 
upper part of the thallus projects far beyond the growing point, 



A. 



which is pushed under 
toward the ventral side. 
A similar condition is 
found in the archegonial 
receptacles of other 
forms, where this in- 
cludes the growing point 
of the shoot (Fig. 21). 
In Targionia the lacunae 
are formed much as in 
Fimhriaria, but they are 
shallower and much wid- 
er, and the pores corre- 
spondingly few. The as- 
similative tissue here re- 
sembles that of Mar- 
thantia and others of the 
higher forms. It is 
sharply separated from 
the compact colourless 
tissue lying below it, and 
the cells form short con- 
fervoid filaments more 
or less branched and an- 
astomosing, and except in the central part of the chamber united 
with the epidermal cells. Under the pore, however, the ends 
are free and enlarged with less chlorophyll than is found in 
other cells. 

All of the Marchantiese except the aberrant genera Dumor- 
tiera and Monoclea correspond closely to one or the other of the 
above types in the structure of the thallus, but in the latter the 
air-chambers are either rudimentary or completely absent, and 
the ventral scales are also wanting. Leitgeb ( (7), vi., p. 124) 




Fig. \^.— Fimhriaria Californica. A, Vertical sec- 
tion through the apex of a sterile shoot, show- 
ing the formation of the air-chambers ; x, the 
apical cell, X300; B, similar section through 
an older part of the thallus, cutting through a 
pore, X 100. 



n MUSCINE^— HEPATIC JE— MARCH A\'TI ALES 



4Q 



investigated D. irrigua, whose thallus is characterised by a 
pecuhar areolation composed of projecting ceU i)lates, and 
came to the conclusion that these were the remains of the walls 
of the air-chambers, whose upper parts, with the epidermis, 
were thrown off while still very young. lie had only herlia- 
rium material to work with, Ixit in this he detected traces of the 
epidermis and pores in the younger i)arts. 1 examined with 
some care fresh material of D. trichocephala, from the Hawa- 
iian Islands, and find that in this species, whicli lias a ])erfectly 
smooth thallus without areolations, that no trace of air-cham- 
bers can be detected at any time. Vertical sections through 
the apex show the initial cells to be like those of other Marchan- 
tiaceae, and the succession of segments the same, but no indi- 
cations of lacunae can be seen either near the apex or farther 
back, the wdiole thallus being composed of a perfectly contin- 
uous tissue without any intercellular spaces, and no distinct 
limit between the chlorophyll-bearing and tlie colourless tissue. 
As Dinnortiera corresponds in its fructification with the higher 
Marchantieas, the peculiarities of the thallus are probably t(j 
be regarded as secondary characters, perhaps produced from 
the environment of the plant, and species like D. irrigua would 
form transitional stages between the typical Alarchantiaceous 
thallus and the other extreme found in D. trichocephala. 

Sexual Organs 

The structure and development of the sexual organs are 
very uniform among the Marchantiaceae. In Finihriaria Cali- 
fornica, wdiich is dioecious, the antheridial receptacle forms a 
thickened oval disc just back of the apex. Not infrequently 
(Fig. I, A), when the formation of antheridia begins not long 
before the forking of the thallus, both of the new growing 
points continue to develop antheridia for a time, and the recep- 
tacle has two branches in front corresponding to these. The 
receptacle is covered with conspicuous papilke which mark the 
cavities in which the antheridia are situated. Vertical longi- 
tudinal sections through the young receptacle show antheridia 
in all stages of development, as their formation, like those of 
Riccia, is strictly acropetal. The first stages are exactly like 
those of Riccia, and the primary cell divides into two cells, a 
pedicel and the antheridium proper. The divisions in the lower 



so 



MOSSES AND FERNS 



CHAP. 



cell are somewhat irregular, but more numerous than in Riccia, 
so that the stalk of the ripe antheridium is more massive 
(Fig. i6). In the upper cell a series of transverse walls is 
formed, varying in different species in number, but more than 
in Riccia, and apparently always perfectly horizontal. In 
Marchantia polymorpha Strasburger (2) found as a rule but 
three cells, before the first vertical walls were formed. In an 
undetermined species of Fimhriaria (Fig. 15) probably F. 
Bolanderi, the antheridia were unusually slender, and fre- 
quently four, and sometimes five transverse divisions are formed 
before the first vertical walls appear. Sometimes all the cells 
divide into equal quadrants by intersecting vertical walls, but 
quite as often this division does not take place in the uppermost 





Fig. 15. — Fimhriaria sp. (?). A, Part of a vertical section of a young antheiidial 
receptacle, showing two very young antheridia (J'), X420; B-E, older stages. 



and lowest cell of the body of the antheridium, or the divisions 
in these parts are more irregular. The separation of the cen- 
tral cells from the w^all is exactly as in Riccia, and the lower 
segments do not take any part in the formation of the sperm 
cells, but remain as the basal part of the wall. In Fimhriaria 
the top of the antheridium is prolonged as in Riccia, but in 
Marchantia this is not the case. The wall cells, as the anther- 
idium approaches maturity, are often much compressed, but 
in Targionia hypophylla, where Leitgeb states that this com- 
pression is so great that the cells appear like a simple membrane, 
I found that, so far from this being the case, the cells were 
extraordinarily large and distinct, and filled the whole space 
between the body of the antheridium and the wall of the cavity, 
which in Leitgeb's figures ((7), vi., PI. x.. Fig. 12) is repre- 



II 



MUSCINEJE— HEPATIC JE—M ARC 11 AXTI ALES 



51 



sented as empty. The antheridium becomes sunk in the thallus 
precisely as in Riccia. The sperm cells are nearly cubical and 
the spermatozoid is formed in the usual way. The free 
spermatozoid (Fig. 16, D) shows al-xjut (juc ruid a hrdf com- 
plete turns of a spiral. The cilia are very long-, and the vesicle 
usually plainly evident. 

According to Ikeno (4), in Marclianlia polyiiiorpJia the 
final division, resulting in the pair of s])ermatids, is unaccom- 
panied by a division wall, and this seems also to be the case in 








Fig. i6.—Fimbriaria Californica. A. Longitudinal section of a fully-developed male 
receptacle, X8; B, longitudinal section of a nearly ripe antheridium, Xioo; C, 
young sperm cells, X6oo; D, spermatozoids, X1200. 

Fimbriaria. In the earlier divisions of the sperm-cells, each 
cell shows two centrosomes (Fig. 17, i), and Ikeno does not 
recognise any difference between these and the so-called 
''blepharoplast" of Webber and other recent students of sperma- 
togenesis, who look upon the blepharoplast as a different organ 
from the centrosome. After the final division, each spermatid 
is provided with a single centrosome (blepharoplast), from 
which, later, the cilia arise. 



52 



MOSSES AND FERNS 



CHAP. 



The young spermatid (Fig. 17, 3) is triangular in section, 
and the blepharoplast is situated in the acute angle which later 
forms the anterior end of the spermatozoid. The blepharoplast 
becomes somewhat elongated, and from it grow out the two 
cilia before any marked change is observable in the nucleus. 
(Fig. 17, 5). Before the cilia can be seen, there appears in the 
cytoplasm a round body which stains strongly, but whose origin 
is not clear. This body Ikeno calls the chromatoid *'Neben- 
korper," and says that it does not participate directly in the 
development of the spermatozoid, but ultimately disappears. 
His figures 30 and 31, however, look as if the portion of the 
spermatozoid between the blepharoplast and the nucleus was 
derived from this "nebenkorper," and not from the cytoplasm, 
as he states is the case. 




Fig. 17. — Marchantia polymorpha. Development of the spermatozoid, i, Sperm-cells 
from the young antheridium; 2, final division of the sperm-cell to form the two 
spermatids; 3-7, development of the spermatozoid; b, blepharoplast; p, "neben- 
korper"; (All figures after Ikeno). 



Owing to the very small size of the spermatozoids in 
Marchantia^ it could not be positively demonstrated whether 
there is a cytoplasmic envelope about the nuclear portion of the 
spermatozoid, but it was concluded that such probably is the 
case. 

When the antheridia are borne directly upon the thallus, 
the apical growth continues after antheridia cease to be formed, 
and the receptacle is thus left far back of the growing in point. 
In forms like Targionia, however, where there are special 
antheridial branches, the growth of these is limited, and gener- 
ally ceases with the formation of the last antheridia. The most 



n MUSCINEAi— HEPATIC JE— MARCH AXTI ALES 53 

specialised forms are found in the genus Marcluuitia and its 
allies, where the antheridial receptacle is burnc up(jn a hjng 
stalk, which is a continuation of the branch frc^n which it 
grows, and the receptacle is a Ijrrnicli-systcni. 1 "he growing 
point of the young antheridial l)ranch fcjrks while still very 
young, and this is repeated in (|uick succession, so that there 
results a round disc with a scalloped margin, each indentation 
marking a growing point, and the whole structure being efjuiva- 
lent to such a branch system as is found in Riccia or Anthoceros, 
wdiere the wdiole thallus has a similar rosette-like form. 'Hie 
antheridia are arranged in radiating rows, the youngest (jne 
nearest the margin and the eldest in the centre. In S(jme 
tropical species, e.g., M. geminata, the branches of the receptacle 
are extended and its compound character is evident. 

The discharge of the spermatozoids from the ripe anther- 
idium may take place with great force. In the case of 
Fimhriaria Calif ornica, Peirce (i) found they were thrown 
vertically for more than fourteen centimetres. The mechanism 
involved includes not only the tissues of the antheridium itself, 
but also the cells below the antheridium, and those forming the 
vails of the chambers in which the antheridia are situated. 
These cells, becoming strongly distended with water, exercise 
great pressure upon the antheridium, whose mucilaginous con- 
tents are also strongly distended. The upper wall of the 
antheridium is finally burst, and the contents expelled violently 
through the narrow, nozzle-like opening of the antheridial 
chamber. 

This explosive discharge was first noted by Thuret ( i ) in 
Conocephahis conicus, and has been recently studied in that 
species by King ( i ) and Cavers ( i ) , as well as in several other 
genera. It is much more marked in the dioecious species. 

The archegonia are never sunk in separate cavities, but 
stand free above the surface of the thallus. The simplest form 
may be represented by Targionia. Here the archegonia arise 
in acropetal succession from the dorsal segments of the initial 
cells of the ordinary branches. A superficial cell enlarges and 
is divided as in Riccia into an outer and an inner cell. The 
latter undergoes irregular divisions and its limits are soon lost. 
In the outer cell the divisions occur in the same order as in 
Riccia, but from the first the base of the archegonium is broad 
and not tapering. Strasburger (2) states that in MarcJiantia 



54 



MOSSES AND FERNS 



CHAP. 



there is a division of the outer of the two primary cells by a 
wall parallel to the first, and that the lower one forms the foot 
of the archegonium, and Janczewski ( i ) gives the same account 
of the young archegonium of Pi'eissia commutata. This cer- 
tainly does not occur in Targionia, and to judge from the later 
stages of Fimhriaria Californica, this species too lacks this 




B 




Fig. i8. — Targionia hypophylla. A, Longitudinal section of the thallus, Xioo; ar, 
archegonia; / /. ventral scales; B, median section through a pore, showing the 
assimilating cells (c/) below, X300. 



division. The full-grown archegonium is of more nearly 
uniform thickness than in Riccia, as the venter does not become 
so much enlarged. The neck canal cells are more numerous, 
about eight being the common number, but in Targionia the 
formation of division walls between these is sometimes sup- 



II 



MUSCINE^— HEPATIC JE—MAKCI J AXTI ALES 



55 



pressed (Fig. 19, C), so that this may acojunt for Janczewski's 
error in stating that the number was always four, as the nuclei 
in unstained sections might very easily he (Aciiocjked. The 
cover cells are somewhat smaller than in Riccia and do not 
usually undergo as many divisions, there being seldom nvjre 
than six in all. In Targionia (hig. 23, A), and Strasburger 
((21), p. 418) observed the same in MarcJiaiitia, the ripe n^^ 
shows a distinct ''receptive spot," that is, the upper ])art of the 
unfertilised egg is comparatively free from granular cyto])lasm, 
while the lower part, about two-thirds in Targionia, is much 
more densely granular. The nucleus is not very large and has 
very little chromatin. The nucleolus is large and distinct and 

/ A, 




D 





Fig. 19. — Targionia hypophylla. A, Longitudinal section of the apex of the thallus, 
with young archegonia (ar), X525; x, the apical cell; B, young, C, older archc- 
gonium in longitudinal section; D, cross-section of the archegonium neck, X5-5- 



Stains very intensely. As the archegonium of Targioiiia 
matures, its neck elongates rapidly and bends forward and 
upward, no doubt an adaptation to facilitate the entrance of 
the spermatozoid. A similar curving of the archegonium neck 
is observed in other forms wdiere the archegonium is upon the 
lower side of the receptacle. 

After an archegonium (or sometimes several of nearly 
equal age) is fertilised, the growth in length of the thallus stops. 



56 



MOSSES AND FERNS 



EHAP. 



but there is a rapid lateral growth with results in the formation 
of two valves, which meet in front much like the two parts of 
a bivalve shall, and this involucre completely encloses the devel- 
oping sporogonium. 

In the simplest cases, where the archegonia are borne upon 
a receptacle^ which is raised upon a stalk, e.g.j Plagiochasma, 
Clevea (Fig. 20, A), the receptacle does not represent, accord- 
ing to Leitgeb ( (7), vi., p. 29), a complete branch, but is only a 
dorsal outgrowth of the latter, which may grow out beyond it, 
or even form several receptacles in succession. The first indi- 
cation of the recep- 

2. 



A. 




'■jjrl'jijIlrilJUfl 



tacle is a dorsal prom- 
inence which soon be- 
comes almost hemi- 
spherical, and near the 
_ ^.^ V. hinder margin the first 
archegonium arises, 
without, apparently, 
any special relation to 
the growing point. 
On the lateral margins 
are then formed two 
other archegonia, not, 
however, simultane- 
ously; and finally a 
fourth may be formed 
in front : three or four 
archegonia in all seem 
to be the ordinary 
^ ^, . A 1 •. ^- 1 .• f number. The stalk of 

Fig. 20. — A. Clevea sp. A, longitudinal section of . ^ 

the thallus showing the dorsal origin of the fe- thc rCCCptaclc IS alSO 

male receptacle (J) ; v, the growing point (dia- ^ dorSal aOOenda2"e of 
gram after Leitgeb) ; B, Reboulia hemisphcerica ^^ ° 

(Radd.), longitudinal section of very young re- tllC tlialluS, and nOt 3. 

ceptacle with the first archegonium C^) ; x, the rl i r- p p f COUtinUation 
apical cell, X300 (after Leitgeb). 

of it. 
The next type is that which Leitgeb attributes to Grim al dia, 
Reboulia, Fimbriaria, and some others, but it is not the type 
found in Fimbriaria Calif arnica. In this type the structure of 




• The sporongonial receptacle of the Alarchantiese is sometimes known as 
the Carpocephalum. 



MUSCINE^—HEPA TIC^— MARCH ANTI ALES 



57 



the receptacle and the origin of the archegonia are the same 
^s in that just described; but here the growing point of the 

A B. 





sp 



per ' \^ 



D 





Fig. 21. — Fimhriaria Calif ornica. A, Plant with two fully-grown sporogonial recep- 
tacles, natural size; B, single receptacle, X4; C, the same cut longitudinally, 
showing the sporogonium {sp), enclosed in the perianth {per); D, nearly median 
section of a young receptacle, showing one growing point (x) and an arche- 
gonium {ar) ; L, air-spaces; st, a pore; r, rhizoids, X40; E, the growing point of 
the same with an archegonium, X300; x, the apical cell. 

branch forms the forward margin of the receptacle, and the 
stalk is a direct continuation of the axis of the branch. Upon 



58 MOSSES AND FERNS chap. 

its ventral surface it shows a furrow in which rhizoids are 
produced in great numbers, and this furrow continues along 
the ventral surface of the thallus. 

The highest type is that of Leitgeb's "Compositse." In this 
form the female receptacle is a branch system similar to that 
of the male receptacle of Marchantia. The branching is usually 
completed at a very early period, while the receptacle is almost 
concealed in the furrow in the front of the thallus. A simple 
case of this kind is seen in Fimbriaria Calif ornica (Fig. 21). 
In this case there are four growing points that have arisen from 
the repeated dichotomy of the primary growing point of the 
branch, and each of these gives rise to archegonia in acropetal 
succession, much as in Targionia, but the number of archegonia 
is small, not more than two or three being as a rule formed from 
each apex. The development of the dorsal tissue is excessive 
and the ventral growth reduced to almost nothing, and the 
growing apices are forced under and upward and lie close to 
the stalk, and the archegonia have the appearance of being 
formed on the ventral side of the shoot, although morphologic- 
ally they are dorsal structures. In the common Marchantia 
polymorpha the branched character of the receptacle is empha- 
sised by the development of the ''middle lobe" between 
the branches. These lobes grow out into long cylindrical 
appendages between the groups of archegonia, and give the 
receptacle a stellate form. Usually in M. polymorpha there 
are eight growing points in the receptacle, and of course as 
many groups of archegonia, which are more numerous than in 
any other genus, amounting to a hundred or more in one recep- 
tacle. In Marchantia, as well as some other genera with com- 
pound receptacles, there are two furrows in the stalk, showing 
that the latter is influenced by the first dichotomy. While the 
archegonia, before fertilisation, are quite free, the whole group 
of archegonia, and indeed the whole receptacle, is invested with 
hairs or scales of various forms that originate either from the 
epidermis of the dorsal side, or as modifications of the ventral 
scales. 

The peculiar American genus Cryptomifritini has been 
investigated by Abrams ( i ) and Howe (3), who finds the devel- 
opment of the carpocephalum to agree essentially with that of 
Fimbriaria Calif ornica. Cavers (6, 7, 8), has recently investi- 
gated that of Conocephahis (Fegatella), Reboulia and Preissia. 



II MUSCINE^—HEPA TIC Al— MARCH ANTI ALES 59 

The lacunar tissue is very much develoijed upon the 
receptacles, as are to an especial degree the peculiar cylindrical 
breathing pores. The formation of these begins in the same 
way as the simple ones, being merely tlic original opening to 
the air-space. This seen from the surface shows an opening 
with usually five or six cells surrounding it. Vertical sections 
show that very soon the cells surrounding the pore become 
deeper than their neighbours and project both above and below 
them. In these cells next arise (Fig. 11, A, B) a series of 
inclined walls by which each of the original cells is transformed 
into a row of several cells, and these rows together form a 
curious barrel-shaped body surrounding the pore. The upper 
cells converge and almost close the space above, and this is still 
further diminished by the cuticle of the outer cell wall of the 
uppermost cells growing beyond the cells and leaving simply 
a very small central opening. The rows of cells also converge 
below, and in Fiinhriaria Calif ornica the lowermost cells are 
very much enlarged, and probably serve to close the cavity 
completely at times, and act very much like the guard cells of 
the stomata of vascular plants. In Leitgeb's group of the 
Astroporge, the simple pores of the thallus have the radial walls 
of the surrounding cells strongly thickened, so that the pores 
seen from the surface appear star-shaped. The most special- 
ised of the Marchantiese, i. e., Marchantia, Preissia, etc., have 
the cylindrical pores upon the vegetative part of the thallus as 
well as upon the receptacle, but in the others they occur only 
upon the latter. 

The Sporophyte. 

The first divisions in the embrvo of the Marchantiacese and 
Corsiniaceae are the same as in the Ricciacese, but only the 
upper part (capsule) of the sporogonium develops spores, 
while the rest becomes the stalk and foot. The simplest form 
of capsule is found in the genera Corsinia and Boschia, which 
have been carefully studied by Leitgeb ((7), iv., pp. 45-47). 
In these the embryo, instead of remaining globular as it does in 
Riccia, elongates and very early becomes differentiated into a 
nearly globular upper part, or capsule, and a usually narrower 
basal portion, the foot (Fig. 22). In the capsule at a very 
early period a single distinct layer of outer cells is separated 
from the central group of cells, and forms the wall of the 



6o MOSSES AND FERNS - chap. 

capsule, which in Boschia at maturity develops upon the inner 
cell walls thickened bars. Only a portion of the cells of the 
central part produce spores ; the remainder do not divide after 
the spore mother cells are formed, but remain either as simple 
slightly elongated nourishing cells (Corsmia) or elaters 
(Boschia). 

The other Marchantiacese are much alike, and as Targionia 
was found to be an especially satisfactory form for study, on 
account of the readiness with which straight sections of the 
embryo could be made, it was taken as a type of the higher 
Marchantiales. The first division wall (basal wall) is trans- 
verse, and divides the embryo into two nearly equal parts. 
This is followed in both halves by nearly vertical walls 
(quadrant walls), and these and the basal wall are then 
bisected by the octant walls, so that as in Riccia the young 

embryo is formed of eight nearly equal 
cells. In Targionia, even at this 
period, the embryo is always somewhat 
elongated instead of globular. The 
next division walls vary a good deal in 
different individuals. Fig. 23, C 
shows a very regular arrangement of 
cells, where the first divisions were 
much the same in all the quadrants. 
Here all the secondary walls were 
nearly parallel with the basal wall, and 
intersected the quadrant and octant 
walls ; but quite as often, especially in 
the upper half of the embryo, these 
secondary walls may intersect the basal 
wall. In no cases seen was there any 
indication of a two-sided apical cell 
such as Hofmeister figures for Tar- 

FiG. 22. — Corsinia inarch an- . . , 111 1 • 

tioides. Young sporogo- gwuia, and probably his error arose 
nium, optical section. X300 from a study of forms where the quad- 
^' ^^ ' rant walls were somewhat incHned, in 

which case the intersection of one of the secondary walls with 
it might cause the apex of the embryo to be occupied by a cell 
that, in section, would appear like the two-sided apical cell of 
the Moss embryo. The regular formation of octants was ob- 
served by me in Fimhriaria Calif ornica, and by Kienitz-Gerlofif 




n 



MUSCINE^— HEPATIC JE— MARCH ANTI ALES 



6i 



(i, 2) and others in Marchantia, Grwialdia, and Prcissia, and 
probably occurs normally in all Marchantiaceae. 

After the tirst anticlinal walls are formed in the octants, no 




Fig. 23. — Targionia hypophylla. A, Longitudinal section of the venter of a ripe 
archegonium, Xsoo; B-E, development of the embryo, seen in longitudinal 
median section — B, two-celled, D, four-celled stages, X500 except E, which is 
magnified 150 times; F, median section of the upper part of an older embryo, 
X250. 



definite order could be observed in the succeeding cell divisions, 
especially in the lower half of the embryo. In the upper part 



62 



MOSSES AND FERNS 



:hap. 



periclinal walls appear, but not at any stated time, so far as 
could be made out, and the first ones do not, as Leitgeb asserts, 
necessarily determine the separation of the archesporium, as in 
the Corsiniese. The growth now becomes unequal, the cells in 
the central zone not dividing so actively, a marked constriction 
is formed, and the young sporogonium becomes dumb-bell 
shaped. By this time a pretty definite layer of cells (Fig. 
27,, F) is evident upon the outside of the capsule, but the cells 
of the globular lower part, or foot, are nearly or quite uniform. 
They are larger than those of the capsule, and more transparent. 



Gal. 






Fig. 24. — Targionia hypophylla. A, Median longitudinal section of older embryo 
enclosed in the calyptra (cal), X8o; B, a portion of the upper part of the same 
embryo, X480; the nucleated cells represent the archesporium; C, part of the 
archesporium of a still later stage; el, elaters; sp, sporogenous cells, X480. 



In the latter the wall becomes later more definite, and remains 
but one cell thick until maturity. The arrangement of the cells 
of the archesporium is very irregular, and until the full number 
of these is formed they are all much alike. Just before they 
separate, however, careful observation shows that two well- 
marked sorts of cells are present, but intermingled in a perfectly 
irregular way A part of these cells are nearly isodiametric, 
the others slightly elongated, and the nuclei of the former cells 



II 



MUSCINE^— HEPATIC Ai— MARCH ANTI ALLS 



63 



are larger and more definite than those of the latter. At this 
stage the cells hegin to separate by a partial deliquescence of 
their cell walls, and when stained with Bismarck-brown these 
mucilaginous walls colour very deeply, and the cells are very 
distinct in sections so treated. They finally separate com- 
pletely, and the much-enlarged globular capsule now contains 
a mass of isolated cells of two kinds, globular sporogenous 
cells and elongated elaters. The former now divide into four 
spores, but before the nucleus divides the division of the spores 
is indicated by ridges which project inward and divide the 
cavity of the mother cell much as in the Jungermanniaceae. 
With the first divisions in the embryo the venter of the 





Fig. 25. — Fimbriaria Californica. A, Young, B, older embryo in median section. A, 
X300; B, Xioo; C, upper part of a sporogonium, after the differentiation of the 
archesporium, X200. 



archegonium, which before was only one cell thick, divides by 
a series of periclinal walls into two layers of cells, which later 
undergo further divisions, so that the calyptra surrounding the 
older capsule may consist of four or more layers of cells. The 
neck of the archegonium remains unchanged, but the tissue of 
the thallus below the archegonium grows actively, and sur- 
rounds the globular foot, which has grown down into the thallus 
for some distance, and only the capsule remains within the 
calyptra. This large growth of the foot is at the expense of 
the surrounding cells of the thallus, which are destroyed by its 



64 



MOSSES AND FERNS 



CHAP. 



growth, and through the foot nourishment is conveyed from 
the thallus to the developing capsule. That is, the sporogo- 
nium is here a strictly parasitic organism, growing entirely at 
the expense of the thallus. 

The further grow^th of the spores and elaters was studied in 
Fimbriaria Calif ornica. The spores remain together in tetrads, 
until nearly ripe. In sections parallel to the surface of the 
younger spores (Fig. 26, C) the outer surface of the exospore 
is covered with very irregular sinuous thickenings, at first 
projecting but little above the surface, but afterward becoming 
in this species extraordinarily developed. In sections of the 




D. 











FiG. 26. — Fimbriaria Californica. A, Young elater X6oo; B, a fully-grown elater, 
X300; C, surface view of the wall of a young spore, showing the developing 
episporic ridges, X6oo; D, section of a wall of a ripe spore, X300. 



ripe spore (Fig. 26, D) three distinct layers are evident, the 
cellulose endospore, the thick exospore, and this outer thick- 
ened mass of projecting ridges which has every appearance of 
being deposited from without, and must therefore be charac- 
terised as epispore (perinium) ; Leitgeb ((7), vi., p. 45) dis- 
tinctly states that thickenings of this character do not occur in 
the Marchantieae, but that the thickenings are always of the 
character of those in Riccia. 



II MUSCINEAi— HEPATIC JE— MARCH AXTI ALES 65 

The elaters are at first elongated tliin-w ailed cells with a 
distinct although small nucleus, and ncarl\ uniformly granular 
cytoplasm. As they grow the cytoplasm loses this unif(jrm 
appearance, and a careful examinaticju, especially of sections, 
shows that the granular part of the cytoplasm begins to form 
a spiral band, recalling somewhat tlie chloro])hyll band of 
Spirogyra. This is the beginning of the characteristic spiral 
thickening of the cell wall, and while at first irregular, the 
arrangement of the granular matter becomes more definite, and 
following the line of this spiral band of granules in the cyto- 
plasm, there is formed upon the inner surface of the wall the 
regular spiral band of the comi)lete elater. Hiis band, which 
is nearly colourless at first, becomes yellow in the mature elater, 
and in Targionia, wdiere there are generally two, they are 
almost black. Not infrequently branched elaters are found, 
but these are unicellular, and no doubt owe their peculiar form 
to their position between the spore mother cells in the young 
archesporium. An axial row^ of granules, which seem to be 
of albuminous nature, remains in the elaters of Fiuihriaria 
until maturity. 

The differences in the structure of the sporogonium in 
different genera of the Marchantieae are slight. In Marchantia 
polymorpJia, the young sporogonium is nearly globular, and 
even when full grown it is ellipsoid with the stalk and foot 
quite rudimentary. Most forms, however, have the foot large, 
but the stalk, compared w^ith that of most Jungermanniace?e, is 
short. In most of them the wdiole of the upper half of the 
young embryo develops into the capsule, but in Fiuihriaria 
Calif ornica I found that the archesporium was smaller than in 
other forms described, and that sometimes the apical part of 
the sporogonium w^as occupied by a sort of cap of sterile cells 
(Fig. 25, C). 

When ripe, the cells of the capsule-wall in Targionia de- 
velop upon their walls dark-colored annular and spiral thicken- 
ings much like those of the elaters. These thickenings are 
quite w^anting in Fimhriaria. 

The dehiscence of the capsule is either irregidar. e.g.. 
Targionia, or by a sort of lid, e.g., Grimaldia, or by a number 
of teeth or lobes, e.g., Liinnlaria, Marchantia. In some forms 
after fertilisation there grows up about the archegonium a cup- 
shaped envelope, "perianth, pseudoperianth," which in Fini- 
6 



^ 



MOSSES AND FERNS 



CHAP, 



briaria especially is very much developed, and projects far 
beyond the ripe capsule (Fig. 21). 

The germination of the spores corresponds in the main with 
that of Riccia. Except in cases where the exospore is very 
thin, in which case it is not ruptured regularly, the exospore 
either splits along the line of the three converging ridges upon 




Fig. 27. — Targionia hypophylla. Germination of the spores, X about 200. In B two 
germ tubes have been formed; C and E are optical sections; x, apical cell; r, 
primary rhizoid; sp, spore membrane. 



the ventral surface, and through this split the endospore pro- 
trudes in the form of a papilla, as in Riccia; or in Targionia 
(Fig. 27) the exospore is usually ruptured in two places on 
opposite sides of the spore, and through each of these a filament 
protrudes, one thicker and containing chlorophyll, the other 
more slender and nearly colourless. The first is the germ tube, 
the second the first rhizoid. In Fimhriaria Californica the 
first rhizoid usually does not form until a later period. In 
Targionia a curious modification of the ordinary process is 
quite often met with (Fig. 27, B). Here, by a vertical divi- 
sion in the very young germ tube, it is divided into two similar 
cells, which both grow out into germ tubes. Whether 
both of these ever produce perfect plants was not determined, 
but the first divisions in both were perfectly normal. The 
first divisions in the germ tube are not quite so uniform as in 



II MUSCINE^—HEPA TIC JE— MARC HAN TI ALES 67 

Riccia trichocarpa, but resemble them very closely In the com- 
moner forms. 

In Fiinhriaria especially, and this has also been observed 
in Marchantia (Leitgeb (7), vi., PL ix., Fig. 13) and other gen- 
era, a distinct two-sided apical cell is usually developed at an 
early period, and for a time the growth of the young plant is due 
to the segmentation of this single cell. Finally this is replaced 
by a single four-sided cell (Fig. 29, C), very much like the 
initial cell of the mature thallus. The young plant, composed 
at first of homogeneous chlorophyll-bearing cells, grows rapidly 
and develops the characteristic tissues of the older thallus. 
The first rhizoids are always of the simple form, and the 

papillate ones only arise later, 
as do the ventral scales. Tar- 
gionia shows a number of pe- 
culiarities, being much less 
uniform in its development 
than Fimhriaria. While it 
often forms the characteristic 
germ tube, and the divisions 
there are the same as in Riccia 
and Fimhriaria, the formation 
of a germ tube may be com- 
pletely suppressed, and the 

Fig. 2S.—Targionia hypophylla. Germ flj-St rCSUlt of gCrmiuatioU is 
plant in which the thallus (T) has ^ - , . , 

been formed secondarily, X260. Often a CCll maSS, from whlCh 

later a secondary germ tube 
may be formed with the young plant at the apex (Fig. 28). 
Such cases as these are the only ones where it seems really 
proper to speak of the plant arising secondarily from a proto- 
nema, for in other cases, as in Riccia, the growth is perfectly 
continuous, and the axis of the young thallus is coincident 
with that of the germ tube, and in no cases observed by me 
could it in any sense be looked upon as a secondary lateral 
growth. 

Biology of the Marchantiaceae 

While the Marchantiaceae are, as a rule, moisture-loving 
plants, still some of them are markedly xerophilous. Most of 
the commoner Calif ornian species, e.g., Fimhriaria Calif ornica, 
Targionia hypophylla, Cryptomitriiim tencnim, dry up com- 






Fig. 29. — Fimhriaria Calif ornica. A, B, Young plants in optical section, showing the 

single two-sided apical cell (x), X260; C, horizontal section of an older plant 

with a single four-sided initial {x), X42S; D, E, two young plants, D from 
below, E from the side, X8s. 



II MUSCINE^— HEPATIC JE— MARCH ANTI ALES 69 

pletely during the long rainless summer, and revive imme- 
diately with the advent of the autumn rains. In these species, 
the growing point of the thallus, with a good deal of the 
adjacent tissue, survives, and at once becomes fresh and active. 
The scales and mucilage-cells found about the apex are doubt- 
less water conservers, and according to Cavers (3, 6, 7), the 
tuberculate rhizoids are also concerned in holding water. In 
Fimbriaria Calif ornica, even the young antheridia survive the 
long summer drought. 

It has been shown (Cavers (6, 7)), that the large hyaline 
cells terminating the green assimilating filaments in the air- 
chambers of such forms as Conoccphalus and Targionia are the 
principal agents in the transpiration of water from the under- 
lying tissues. 

Besides the formation of definite gemmae like those of 
Marchantia and Lumilaria, the thallus in most Marchantiaceae 
is capable of extensive regeneration, even from small frag- 
ments. In Conoccphalus there have also been found tuberous 
outgrowths, which are formed under certain conditions and 
are doubtless for propagation (Cavers (6)). 

The Marchantiaceae are readily separable into two sub- 
families, the Targioniese, and the Marchantiese. Leitgeb 
has made a further division of the latter family, but some of 
the characters given are not sufficiently constant to warrant 
his division, and for that reason it has been thought best not 
to accept them. Thus Fimbriaria Calif ornica, which is, in 
regard to its fructification, typical, has the female receptacle 
of the composite type, a character which, according to Leitgeb, 
not only does not belong to the genus Fimbriaria, but is not 
found in any genus of the group (Operculatcc) to which he 
assigns it. This species too does not have the capsule opercu- 
late, but opens irregularly. 

The Targioniese include the two genera Targionia, which 
has been already described at length, and CyatJwdium (Leitgeb 
(7), vi., p. 136), whose development is not sufficiently known 
to make its systematic position quite certain. In the position 
of the sexual organs, and the formation of the two-valved 
involucre about the fruit, as well as the position of the latter, it 
corresponds closely to Targionia, but the structure of the thallus 
is extraordinarily simple, there being practically but two layers 
of cells with large irregular air-chambers between. While two 



70 MOSSES AND FERNS chap. 

sorts of rhizoids are present, those that represent the papillate 
type of the other Marchantiacese, while thicker walled than 
the others, do not develop the projecting prominences. Indeed 
the whole structure of the plant is curiously reduced, and 
Leitgeb describes it as resembling the young plants of Mar- 
chantia or Preissia. The development of the sexual organs is 
but imperfectly known, and the suggestion of Leitgeb's that 
possibly the antheridium is reduced to a single cell, seems hardly 
probable in view of the structure of the rest of the plant. The 
sporogonium has the stalk and foot exceedingly rudimentary, 
but the upper part of the capsule shows a zone of cells whose 
walls are marked by peculiar ring-shaped thickenings, and opens 
regularly by a number of teeth, which on account of the thick- 
ened bars upon the cell wall offer a superficial resemblance to 
the peristome of the Bryales. As in Targionia the archegonia 
arise near the apex of the ordinary shoots, and no proper 
receptacle is formed. 

All of the other forms have the archegonia borne upon a 
special receptacle, which, as the sporogonia develop, is raised 
upon a stalk. Here belong, according to Schiffner ( i ) sixteen 
genera with about 150 species. The receptacle may be, as we 
have seen, strictly dorsal in origin, or it may include the grow- 
ing point of the archegonial branch, or finally it may be a 
branch system arising from the repeated dichotomy of the 
original growing point. 

MONOCLEA 

The genus Monoclea includes two known species, M, 
Forsteri, found in New Zealand and Patagonia, and M, 
Gottschei, of Tropical America, said also to occur in Japan. 
This genus has been usually associated with Jungermanniales 
(Leitgeb (7), vol. iii., Schiffner (i)), but a more complete 
study of the plant has shown that its affinities are undoubtedly 
more with the simpler Marchantiacese. The structure and posi- 
tion of the sexual organs, especially the antheridia, and the 
development of the sporophyte, so far as it has been made out 
(Cavers (7), Johnson (3)), all point unmistakably to a rela- 
tionship with the Marchantiacese. 

Two kinds of rhizoids are present, although not so marked 
as in the typical Marchantiacese, but the thallus lacks the char- 



II MUSCINEJE—HEPA TIC^— MARCH ANTI ALES 71 

acteristic lacunar tissue of these forms. In the latter respect 
Monoclea closely resembles Diimortiera, and as in that genus, 
the absence of the air-chambers may be attributed to the semi- 
aquatic habit of the plant. Monoclea evidently belongs to the 
lower series of Marchantiaceae, and may perhaps be compared 
to Targionia. See Ruge (i), Cavers (7), Campbell (19). 

Resume of the Marchantiales 

Comparing the different members of this order, one is struck 
by the almost imperceptible gradations in structure between the 
different families, and this accounts for the difference of opinion 
as to where certain genera belong. That the Ricciacese cannot 
be looked upon as a distinct order is plain, and they may perhaps 
be best regarded as simply a family co-ordinate with the Cor- 
siniese and Targionieae, and not a special group opposed to all 
the other Marchantiaceae. The gradual increase in complexity 
of structure is evident in all directions. First the thallus passes 
by all gradations from Riccia — with its poorly defined air- 
chambers with no true pores and single ventral lamellae, 
through Ricciocarpiis and Tessalina, where definite air-cham- 
bers are present, opening by pores of the same form as those of 
the lower Marchantieae, and separate ventral scales occur — to 
forms like Marchantia, where the air-chambers are verv definite 
and contain a special assimilating tissue, and the pores are of 
the cylindrical type. With this differentiation of the thallus 
is connected the segregation of the sexual organs and the devel- 
opment of special receptacles upon which they are borne. 
Finally, in the development of the sporogonium, while there is 
almost absolute uniformity in the earlier stages, we find a 
complete series of forms, beginning w^ith Riccia, where no stalk 
is developed and all the cells of the archesporium develop spores, 
ascending through Tessalina, with a similar absence of a stalk, 
but the first indication of sterile cells, through the Corsinieco, to 
forms with a massive foot and elaters fully developed. It 
may be said, however, that there is no absolute parallelism be- 
tween the development of the gametophyte and that of the 
sporophyte; for in Marchantia, the most specialised genus as 
to the gametophyte, the sporogonium is less developed than in 
the otherwise simpler Targionia and Fimbriaria. 



CHAPTER III 

THE JUNGERMANNIALES 

A VERY large majority of the Hepaticse belong to the 
Jungermanniales, which show a greater range of external dif- 
ferentiation than is met with in the Marchantiaceae, but less 
variety in their tissues, the whole plant usually consisting of 
almost uniform green parenchyma. In the lowest forms, e.g., 
Aneiira and Metzgeria, the gametophyte is an extremely simple 
thallus, in the former composed of almost perfectly similar 
cells, in the latter showing a definite midrib. Starting with 
these simplest t3^pes, there is a most interesting series of transi- 
tional forms to the more specialised leafy ones, where, however, 
the tissues retain their primitive simplicty. All of the Junger- 
manniales grow from a definite apical cell, which differs in 
form, however, in different genera, or even in different species 
of the same genus. Rhizoids are usually present, but always 
of the simple thin-walled type. 

The gametophyte, with the exception of the genera Haplo-. 
mitrium, and Calohryum, is distinctly dorsiventral, and even 
when three rows of leaves are present, as in most of the foliose 
forms, two of these are dorsal and lie in the same plane, while 
the third is ventral. In the thallose forms, while the bilaterality 
is strongly marked, there is not the difference between the 
tissues of the dorsal and ventral parts which is so marked in 
the Marchantiales. In the lowest forms the gametophyte is a 
simple flat thallus fastened to the substratum by simple rhizoids, 
and develops no special organs except simple glandular hairs 
which arise on the ventral side near the apex, and whose muci- 
laginous secretion serves to protect the growing point. In 
Blasia and Fossomhronia we have genera that while still retain-^ 
ing the flattened thalloid character, vet show the first formation 

73 



Ill ^ THE JUNGERMANNIALES 73 

of lateral appendages which represent the leaves of the true 
foliose forms. In the latter the axis is slender, and the leaves 
usually in three rows and relatively large. 

The archegonia correspond closely in their development to 
those of the Marchantiaceae, and in tlie lower (anacrogynous) 
forms arise in much the same way from surface cells of the 
dorsal part of the younger segments, and the apical cell is not 
directly concerned in their formation. The archegonia in these 
thus come to stand singly or in groups upon the dorsal surface 
of the thallus, wdiose growth is not interrupted by their develop- 
ment. In the higher leafy forms (Jungermanniacese acro- 
gynae) they occur in groups at the end of special branches, 
whose apical cell finally itself becomes the mother cell of an 
archegonium, and with this the growth in length of the branch 
ceases. 

The antheridia in most cases dififer essentially in their first 
divisions from those of the Marchantiaceas. After the first 
division in the mother cell, by wdiich the stalk is cut off from the 
antheridium itself, the first wall in the latter, in all forms inves- 
tigated except Sphcerocarpus, Riella and Geothallus, is 
vertical, instead of horizontal, and the next formed walls are 
also nearly vertical. The ripe antheridium is usually oval in 
outline and either nearly sessile or provided with a long pedicel. 
The spermatozoids are as a rule larger than in the Marchan- 
tiales, and show more numerous coils, but like those of the lat- 
ter, are always biciliate. 

The embryo differs in its earliest divisions from that of the 
Marchantiacege. The first transverse wall divides the embryo 
into an upper and lower cell, but of these the lower one usually 
takes no further part in the development of the sporogonium, 
but either remains undivided or divides once or twice to form a 
small appendage to the base of the sporogonium. In the upper 
cell the first wall may be either vertical {e. g., P cilia and most 
anacrogynous forms), or it may be transverse. From the 
upper of the two primary cells not only the capsule but the seta 
and foot as well are formed. The development of these differ- 
ent parts varies in different forms, and will be taken up when 
considering these. 

.. - All of the Jungermanniales, except the Anelatereae, possess 
perfect elaters, but in the latter these are represented merely by 
sterile cells that probably serve simply for nourishing the grow- 



74 MOSSES AND FERNS chap. 

ing spores. The sporogonium remains within the calyptra 
until the spores are ripe, when by a rapid elongation of the cells 
of the seta it breaks through the calyptra, which is left at its 
base, and the capsule then opens. The opening of the capsule 
is usually effected by its walls splitting into four valves along 
lines coincident with the first formed vertical cell walls in the 
young embryo. These valves, as well as the elaters, are 
strongly hygroscopic, and by their movements help to scatter 
the ripe spores. The latter show much- the same differences 
observed in the Marchantiaceae. When the spores germinate 
at once they have abundant chlorophyll and a thin exospore, but 
where they are exposed to drying up, they have no chlorophyll 
and the exospore is thick and usually with characteristic thick- 
enings upon it. From the germinating spore the young 
gametophyte may develop directly, or there may be a well- 
m.arked protonemal stage. This latter is always found in the 
foliose forms, and is either a flat thallus, like the permanent 
condition of the lower thallose genera, or sometimes (Proto- 
cephalozia) it is a branched filamentous protonema, very much 
like that of the Mosses, and sometimes long-lived and produc- 
ing numerous gametophores. 

Non-sexual reproductive bodies in the form of unicellular 
gemmae are found in many species, and in Blasia special 
receptacles with multicellular gemmae something like those of 
Marchantia occur. 

The Jungermanniales naturally fall into two well-marked 
series,^ Anacrogyn^e and Acrogynae, based upon the position 
of the archegonia. These in the former are never produced 
directly from the apical cell of a branch, in the latter group 
the apical cell of the archegonial branch always sooner or later 
becomes transformed into an archegonium. The Haplomitriese 
show some interesting intermediate forms between the two 
groups, but all the other Jungermanniales examined belong 
decidedly to one or the other. As a rule the Anacrogynae are 
thallose (the "frondose" forms of the older botanists), but a 
few genera, especially Fossomhronia, show a genuine formation 
of leaves. All the Acrogynae have a distinct slender stem with 
large and perfectly developed leaves. 

' Prof. L. M. Underwood proposes the name Metzgeriaceas fOr the Ana- 
crogynse, reserving the name Jungermanniaceae for the Acrogynae. These 
two groups he considers co-ordinate with the Marchantiales and Antho- 
cerotes. 



Ill THE JUNGERMANNIALES 75 

ANACROGYN^ 

Jungermannlales Anacrogynae. Apical cell of female axis 
never becoming transformed into an archegonium. 

A. Anelatereae. No true elaters, but sterile cells repre- 
senting these. Capsule cleistocarpous. Four genera, 
T hallo car pus, Sphcerocarpus, Riella, Gcothallus. 

B. Elatereae. Capsule opening either by four valves or 
irregularly. Elaters always developed. 

a. Gametophore always dorsiventral, either strictly 
thallose or with more or less developed leaves. Fam- 
ilies, — Metzgerieae, Leptothecese, Codoniese. 

b. Gametophore upright with three rows of radially ar- 
ranged leaves. Fam. I., Haplomitrieae. 

Anelatere^ 

The simplest form belonging here is Sphcerocarpus, a genus 
that shows certain affinities with the Ricciacese, but on the 
whole seems to be more properly placed at the bottom of the 
series of the Jungermannlales. 

Sphcerocarpus terrestris occurs in Europe and the south- 
eastern United States. In California it is replaced by two 
species, 6^. Calif orniciis and S. cristatits, which until recently 
(Howe (3)) were not recognised as distinct, and were con- 
sidered to be a variety of S. terrestris. They are small plants 
growing upon the ground, usually in crowded patches, where, 
if abundant, they are conspicuous by the bright green colour of 
the female plants. The males are very much smaller, often less 
than a millimetre in diameter, and purplish in colour, so that 
they are easily overlooked. The thallus is broad and passes 
from an indefinite broad midrib into lateral wings but one 
cell in thickness (Fig. 30). The forward margin is occupied 
by a number of growing points formed by the rapid dichotomy 
of the original apex, and separated only by a few rows of cells. 
From the lower side of the thallus grow numerous rhizoids 
of the thin-walled form. The whole upper surface is cov- 
ered with the sexual organs, each of which is surrounded by 
its own very completely developed envelope. 

A vertical section passing through one of the growing 
points (Fig. 30, C) shows a structure closely like a similar 
section of Riccia. The apical cell {x) produces dorsal and 



1^ 



MOSSES AND FERNS 



CHAP. 



ventral segments, and from the outer cells of the former the 
sexual organs arise exactly as in Riccia. On the ventral sur- 
face the characteristic scales of Riccia are absent, and are re- 
placed by the glandular hairs found in most of the anacrogy- 
nous Jungermanniales. 

The development of the archegonium shows one or two 
peculiarities in which it differs from other Hepaticse. The 
mother cell is much elongated, and the first division wall, by 

c $ 




Fig. 30. — Sphcerocarpus Californicus (?). A, Male plant, X40; ^, antheridia; B, 
median section of a similar plant, X80; C, the apex of the same section, X240; 
h, ventral hair. 



which the archegonium itself is separated from the stalk, is 
some distance above the level of the adjacent cells of the 
thallus, so that the upper cell is very much smaller than the 
lower one. The upper cell has much denser contents than the 
lower one, which instead of remaining undivided as in Riccia, 
divides into two nearly equal superimposed cells, this division 



Ill 



THE JUNGERMANNIALES 



77 



taking place about the same time as the first division in the 
archegonial cell (Fig. 31, B). The divisions in the latter are 
the same as in Riccia, and the general structure of the arche- 
gonium offers no noteworthy peculiarities. The number of 
neck canal cells is small, probably never exceeding four, and in 
this respect recalls again Riccia. The central cell is relatively 
large, and the ventral canal cell often nearly as large as the 
Qgg. As the archegonium develops, its growth is stronger on 
the posterior side, and it thus curves forward. At first the 
young archegonium projects free above the surface, but pres- 




FiG. 31. — Sphcrrocarpus sp. (?). Development of the archegonium. A-C, Longi- 
tudinal sections, X6oo; D, X300. 



ently an envelope is formed about it exactly as in Riccia, but 
arising at a later stage. After this has begun to form, its 
growth is very rapid, and it soon overtakes the archegonium 
and grows beyond it, and finally forms a vesicular body, plainly 
visible to the naked eye, at the bottom of which the arche- 
gonium lies. The formation of this involucre is quite inde- 
pendent of the fertilisation of the archegonium, and as these 
peculiar vesicles cover completely the whole dorsal surface of 
the plant, they give it a most characteristic appearance. Usu- 
ally each archegonium has its own envelope, but Leitgeb ( (7), 



78 MOSSES AND FERNS chap. 

iv., p. 68) states that two or even more may be surrounded 
by a common envelope. When ripe, the venter of the arche- 
gonium is somewhat enlarged, but not so much as in Riccia. 
The egg-cell is very large, oval in form, and nearly fills the 
cavity of the single-layered venter. 

The first wall in the embryo is transverse, and divides the 
egg cell, which before division becomes decidedly elongated, 
into two nearly equal cells. Ordinarily in each of these cells 
similar transverse walls are formed before any vertical walls 
appear, so that the embryo consists of a simple row of cells. 
As in the Marchantiaceae the first wall separates the future 
capsule from the stalk, and in this respect Sphcerocarpus 
approaches the Marchantiales rather than the Jungermanni- 
ales. Following the transverse walls there are formed in all 
the upper cells nearly median vertical ones, which are inter- 
sected by similar ones at right angles to them, so that in most 
cases (although this is not absolutely constant) the upper half 
of the young sporogonium at this stage (Fig. 32, A) consists 
of two tiers, each consisting of four cells. The lower part of 
the embryo is pointed, and the basal cell either undergoes no 
further division or divides but once by a transverse wall, and 
remains perfectly recognisable in the later stages (Fig. 32, B, 
C). The other cells of the lower half divide much like those 
of the upper half, but the divisions are somewhat less regular. 

There next arise in all the cells of the upper half periclinal 
walls, which at once separate the wall of the capsule from the 
archesporium. This wall in the later stages (Fig. 32, C, D) is 
very definite, and remains but one cell thick up to the time the 
sporogonium is mature. The further divisions in the capsule 
are without any apparent order, and result in a perfectly glob- 
ular body composed of an outer layer of cells enclosing the 
archesporium, which consists of entirely similar cells with 
rather small nuclei and dense contents. While these changes 
are going on in the capsule, the lower part of the embryo loses 
its originally pointed form, and the bottom swells out into a 
bulb (the foot), which shows plainly at its base the original 
basal cell of the young embryo. This bulb is characterised by 
the size of the cells, which are also more transparent than those 
of the other parts of the embryo. 

Owing to the development of the stalk of the archegonium, 
after fertilisation the whole embryo remains raised above the 



Ill 



THE JUNGERMANNIALES 



79 



level of the thallus, instead of penetrating into it, as is usually 
the case. The stalk or portion between the capsule and foot 
remains short, and in longitudinal section shows about four 






D. 




Fig. 32. — SphcBrocarpus sp (?). A, B, Median longitudinal sections of the arche- 
gonium venter, with enclosed embryos, X260; C, an older sporogonium in median 
section, X260; D, a still later stage, showing the large space between the arche- 
sporial cells and the wall, X8s. 



rows of cells. As the calyptra grows the upper part becomes 
divided into two layers, the part surrounding the foot into 
three. Instead of breaking through the calyptra at maturity, 



8o MOSSES AND FERNS chap. 

the capsule grows faster than the calyptra long before it is 
mature, and the upper part of the calyptra is first compressed 
very much and finally completely broken through by the en- 
larging capsule. 

Leitgeb calls attention to the fact that soon after the 
cells of the archesporium begin to separate, the whole mass 
of cells becomes completely separated from the wall of the 
capsule, which grows rapidly until the cavity w^ithin is much 
larger than the group of archesporial cells, which thus float 
free in the large cavity. Fig. 32, D shows a section through 
a sporogonium at this stage. The cells making up the central 
mass are apparently alike, but in the living sporogonium part 
of the cells have abundant starch and chlorophyll, while in the 
others these are wanting or present in much less quantity, 
while their place is taken by oil, but no rule could be made 
out as to the distribution of the two sorts of cells. The latter 
are the spore mother cells, while the others are gradually used 
up by the developing spores. The spores in S. terrestris remain 
united in tetrads, and escape from the capsule by the gradual 
decay of its wall and of the surrounding tissue of the gameto- 
phyte. 

The male plants are very much smaller than the females, 
with which they grow and under which they are at times 
almost completely hidden. The cell walls of the antheridial 
envelopes are often a dark purple-red colour, and this makes 
them much harder to see than the vivid green female plant. 
The apical growth and origin of the antheridium is the same 
as in Riccia. The first division in the primary antheridial 
cell is the same as in that of the archegonium, but the basal 
cell is smaller, and does not divide again transversely, and 
takes but little part in the formation of the stalk. In the an- 
theridium mother cell are next formed two transverse walls, 
dividing it into three superimposed cells. The two uppermost 
divide, as in the Marchantiacese, by vertical median walls into 
regular octants, the lower by a series of transverse walls into 
the stalk, which consists of a single row of cells sunk below the 
level of the thallus. After the division of the body of the 
antheridium into the octant cells, periclinal Avails are formed 
in each of these, so that the body of the antheridium consists 
of eight central cells and eight peripheral ones, and the stalk 
of two cells, of which the upper one forms the base of the 



Ill 



THE JUNGERMANNIALES 



8i 



antheridium body (Fig. 33, D). At this stage and the one 
preceding it SpJiccrocarpiis recalls the structure of the anther- 
idium of the Charace?e, although the succession of walls is 
not exactly the same. The divisions of the central cells are ex- 
tremely regular, walls being formed at right angles, so that 
the sperm cells are almost perfectly cubical, and the limits of 
the primary central cells are recognisable for a long time. 

The development of the antheridial envelope begins much 
earlier than that about the archegonium, but in exactly the 
same w'ay. By the time that the wall of the antheridium is 
formed the envelope has already grown up above its summit, 
and as the antheridium develops it extends far beyond it like 
a flask, at the bottom of which the antheridium is placed, and 
through whose neck the spermatozoids escape. These are 

A B £ 




Fig. 33. — Sphcerocarpus sp (?). Development of the antheridium. A-D, Median lon- 
gitudinal sections, X450; E, an older one, X22S', F, a spermatozoid, killed with 
osmic acid, X900. 



very much like those of the other Hepaticae, and in size exceed 
those of most of the Marchantiaceae, but are smaller than is 
usual among the Jungermanniales. 

Leitgeb studied the germination of the spores in ^. tcrres- 
tris, which remain permanently united in tetrads. He found 
that all the spores of a tetrad were capable of normal develop- 
ment, W'hich does not differ from that of Riccia or other thal- 
lose Liverworts. A more or less conspicuous germ tube is 
found at the end of which the young plant develops, one of the 
octants of the original terminal group of cells becoming, appar- 
ently, the apical cell for the young plant. The latter rapidly 

grows in breadth and soon assumes all the characters of the 
6 



§2 



MOSSES AND FERNS 



CHAP. 



older plant. Leitgeb (Fig. 17, PI. IX.) shows a condition 
that looks as if at an earlier stage a two-sided apical cell had 
been present, but he says nothing in regard to this. The 
sexual organs appear while the plant is extremely small. Leit- 
geb says he observed the first indications of them on individ- 
uals only one millimetre in diameter, and before the first papil- 
late hair on the ventral surface had been formed. 

In the commonest Californian species, ^. cristatus the 
spores separate completely at maturity. The early stages of 
germination are like those in S. terrestris. There is usually 
a two-sided apical cell at first, which later is replaced by the 
type found in the adult thallus. 




^^yi\wi^ 



Fig. 34. — Geoihallus tuberosus. A, Male plant, X15; B, section of female plant, X15; 

/. young tuber. 



Where there is an excess of moisture the thallus may be- 
come much larger than usual, this being especially noticeable 
in the male plants. There is often, under these conditions, 
a development of leaf-like marginal lobes. This excessive 
vegetative development of the thallus is accompanied by a 
marked diminution in the number of the sexual organs. 
(Campbell (17)). 

Geothallus. 

Evidently closely allied to Sphcerocarpus is a remarkable 
Liverwort, as yet found only near San Diego, in Southern 



Ill 



THE JUNGERMANNIALES 



83 



California (Campbell (18)). Geothallus tiiherosiis (Figs. 
34, 35), differs from Sphccrocarpus in its much larger size, 
the development of leaf-like organs, much like those of Fos- 
somhronia and by the very much larger size of the spores. 
There are also some minor differences in the structure of the 
reproductive organs, the antheridia having a more massive 
pedicel than that of Sphccrocarpus. The plants are perennial, 
and at the end of the growing season the younger parts of the 
thallus become changed into a tuber with a thick black cover- 
ing. The tubers are buried in the earth during the dry season. 




n 



Fig. z^.— Geothallus tuberosus. A, Archegonium, X200; B, ripe antheridium, X about 
65; C, a four-celled embryo, X200; D, ripe spore; E, sterile cells, X 100. 

The apex of the shoot persists and resumes growth as soon 
as the conditions are favorable. 



Riella. 

The peculiar genus Riella (Goebel (17), Leitgeb (7), Por- 
sild (i)), while it closely resembles Sphccrocarpus in the struc- 
ture of the reproductive organs and sporophyte, differs very 
much in the habit of the gametophyte. Until very recently 
(Howe and Underwood (3)), all the species known were 
from the regions adjacent to the Mediterranean, but one species 
has since been found in the Canary Islands, and another in the 
United States. They are all submersed aquatics. The thal- 
lus shows a cylindrical axis, from which grows a thin vertical 



84 



MOSSES AND FERNS 



CHAP. 



dorsal lamina or wing, which may be more or less spirally 
placed, owing to torsion of the axis, but this torsion was much 
exaggerated in the early figures of the original species, R. 
helicophylla. According to Goebel's investigations, the grow- 
ing point is formed secondarily, and this statement is con- 
firmed by Howe's studies. The latter writer has studied the 
germination of the spores and has described the formation of 
gemmae in R. Americana. 

The latest contribution to our knowledge of Riella is that 
of Porsild ( I ) . He confirms Howe's statements and has 





.JL. 



D. 



G 





Fig. 36.— a, D, Riella Americana; B, C, R. helicophylla; A, Apex of female plant, X8; 
B, C, lateral and ventral view of the growing point, Xsoo; x, apical cell; Z,, leaves. 
D, male plant, X I J^ ; CA, D, after Howe ; B, C, after Leitgeb.) 



further investigated the question of the growing point. He 
finds that while an apical cell is absent in the younger stages, 
it is formed later in normal plants. 

Both archegonia and antheridia resemble those of Sphcero- 
carpus very closely, and the structure of the sporophyte is also 
the same, no true elaters being developed, but instead there 
are simply sterile cells. 



Ill 



THE JUNGERMANNIALES 



8S 



Elatereae 

Aneura and Metzgeria represent the simplest of the typical 
anacrogynous Jungermanniales. Jn the former the thallus 
is composed of absolutely similar cells, all chlorophyll-bearing, 
and in each cell one or more oil bodies, like those of the Mar- 
chantiacese. In Mctzgeria (Fig. 37) the wings of the thallus 
are but one cell thick, and there is a very definite midrib, usu- 
ally four cells thick. The apical growth in both genera is 






Fig. 27.—~Metsgeria pubescens. A, Surface view of the thallus in process of division, 
X80; B, growing point of a branch showing the two-sided apical cell (x) and the 
ventral hairs (h), X240; C, the growing point in process of division, x, x', the 
apical cells of the two branches, X480. 

the same, and is effected by the growth of a "two-sided" 
apical cell.^ The segmentation is very regular, especially in 
Met/:geria (Fig. 37), where each of the segments divides first 
into an inner and an outer cell, the former by subsequent divi- 
sions parallel to the surface of the thallus producing the thick- 

- . '■ •  ' ' ^Leitgeb (7), vol. iv. 



86 



MOSSES AND FERNS 



CHAP. 



ened midrib, the outer cells dividing only by perpendicular 
walls, forming the wings. From the ventral surface of the 
young midrib papillae project, which curve up over the grow- 
ing point, in the form of short two-celled hairs, whose end 
cells secrete mucilage for its protection. In Aneura the growth 
is very similar, but all of the cells divide by walls parallel to 
the surface of the thallus, and no midrib is formed, and the 
thallus is several cells thick in all parts. In both genera numer- 
ous delicate colourless rhizoids are developed from the ven- 
tral surface, especially of the midrib, when that is present. 

Aneura is of interest as showing the only case among the 
Bryophytes of structures that may be compared to the zoo- 

A. 





Fig. 38. — A, Symphyogyna sp.; B, Hymenophyton Habellatum, XiJ^; sp., young 
sporophyte; b, young shoot. 



Spores of the Green Algae. In A. multifida Goebel ((8), p. 
337), discovered that the two-celled gemmae which had been 
described as formed simply by a separation of the cells of the 
thallus, were really formed within the cells and expelled from 
them through an opening, after which they divided into two 
cells and ultimately developed a young plant, much as an ordi- 
nary spore would do. The absence of cilia from these cells, 
which probably are the last reminiscences of the ciliated go- 
nidia of the aquatic ancestral forms, is to be accounted for by 
the terrestrial habit of Aneura. 

The branching is dichotomous, and is brought about by 



Ill 



THE JUNGERMANNIALES 



87 



the formation of a second apical cell in one of the youngest 
segments. This apical cell is formed by a curved wall, which 
strikes the outer wall of the segment ( iMg. 37, C). Thus 
two apical cells arise close together, and as segments are cut 
off from each, they are forced farther and farther apart, and 
serve as the growing point of two shoots, which may continue 



A 





Fig. 39. — Aneura pinnatiUda. A, Part of a thallus with two antheridial branches, 
slightly magnified; B, an archegonial branch, X40; C, cells from the margin of 
the archegonial branch showing the oil bodies (0), X300. 



to grow equally, when the thallus shows a marked forking 
(M. furcata), or one of the branches grows more strongly than 
the other, which is thus forced to one side and appears like a 
lateral branch {Aneura pinnatiiida, Fig. 41, B). 

In certain species of Pallavicinia and Symphyogyna, and 
especially in Hymenophyton (Fig. 38, B), the gametophyte 
shows a differentiation into a prostrate rhizome-like sterj, 



88 



MOSSES AND FERNS 



CHAP. 



from which arise upright flattened shoots which are repeatedly 
forked, so that there is a remarkably close superficial resem- 
blance to the fan-shaped leaves of certain Ferns, especially 
some of the smaller Hymenophyllacese. This resemblance is 
heightened by the very distinct midrib traversing each thallus- 
segment. 

Sexual Organs. 

The sexual organs in both Aneura and Met2geria are borne 
on short branches, which in the latter arise as ventral struc- 




FiG. 40.'-^Aneura pinnatiUda. A, Horizontal section of the apex of a young antheridial 
branch, X565; x, the apical cell; (^, antheridia: B, transverse section of a young 
archegonial branch, passing through the apical cell (x) ; J, young archegonia, 
X525; C, longitudinal section of a nearly ripe archegonium, X262; D, E, 
spermatozoids of Pellia calycina, X1225 (D, E, after Guignard). 



tures, but in Aneura are simply ordinary branches that are 
checked in their growth by the production of the sexual or- 
gans, and not infrequently may grow out into ordinary 
branches after the formation of the sexual organs has ceased. 
In A. pinnatifida (Fig. 39, B), archegonia and antheridia are 
usually produced upon separate branches, but may occur to- 
gether. 

The origin of the antheridia can be readily followed in 



Ill THE JUNGERMANNIALES 89 

sections made parallel to the surface of the male branch. The 
apex is occupied by an apical cell of the usual form, and the 
cell divisions in the young segment arc extremely regular. 
The segment first divides into an inner and an (jutcr cell, and 
the former probably next into a dorsal and a ventral fjne. The 
dorsal cell divides by a longitudinal wall into t\v(j nearly equal 
cells, of which the inner one, dividing by a wall perpendicular 
to the first, gives rise to the primary cell of the antheridium 
(Fig. 40, Ac^). This cell now projects above the surface of 
the thallus, and divides into a single stalk cell, which under- 
goes no further divisions, and the antheridium mrjther cell. 
The divisions in the latter correspond to those in the other 
Jungermanniales. First a vertical w^all is formed, dividing 
the young antheridium into two equal parts. Next, in each 
of these, two walls arise intersecting each other as well as- the 
median wall, and dividing each half of the antheridium into 
three cells, two peripheral ones and a central ofie. (A some- 
what later stage than this is shown in Fig. 40, A.) The per- 
ipheral cells do not reach to the top of the antheridium, and 
next a periclinal wall is formed near the top of the central cells, 
by which a third peripheral cell is formed in each half of the 
antheridium, which now consists of two central cells and six 
peripheral ones. The further divisions were not followed in 
detail, but seem to correspond with those in the higher forms. 

Of the two first cells into which the dorsal cell divides, the 
one which does not produce the antheridium together with the 
inner of the two into which that cell first divides, form a par- 
tition w^hich rapidly increase^ in height vvith the growth of 
the antheridia, and separates 'each from its neighbour by a 
single layer of cells, so that the antheridia are sunk in cham- 
bers, arranged in two rows, corresponding to the two series 
of segments of the apical cell. 

In the other thallose anacrogynous forms, c. g., Palla- 
vicinia (Fig. 41, A), the sexual organs are borne upon the 
dorsal surface of the ordinary shoots, usually surrounded by 
a sort of involucre. In most of these forms the apical cell is 
of a different type from that of Anciira, but is variable even 
in the same species. Thus in Pallavicinia cylindrica, while 
the commoner form is nearly wedge-shaped, appearing four- 
sided seen from the surface, and triangular in vertical section, 
it may approach very nearly the two-sided type (Fig. 42, C). 



90 



MOSSES AND FERNS 



CHAP. 



In the ordinary form four sets of segments are cut off, — dorsal 
and ventral, as in Riccia or Sphcerocarpus, and two sets of 
lateral ones. In Pellia calycina the apical cell shows a similar 
form, but in P. epiphylla (Fig. 42, D, E), another type is 
seen. Here, while the surface view is the same as in P. caly- 




B. A 




Fig. 41.— a, Pallavicinia cylindrica, X4; per, the elongated perianth; B, Aneura pin- 
natiUda, X6; J, archegonial branches; C-E, Fossombronia longiseta, X4; F, Blasia 
pusilla, X4. 



cinaj in vertical section the cell is nearly semicircular, i. e., here 
there are but three sets of segments, two lateral ones and a 
basal one, extending the whole depth of the thallus, and only 



m 



THE JUNGERMANNIALE^ 



02 




Fig. 42. — A, Vertical, B, C, horizontal sections through the apex of Pallavicinia 
cylindrica; x, apical cell, A, X225; B, C, X450; D, E, Pellia epiphylla; U, ver- 
tical section; E, horizontal (optical) section, X4S0. 



92 



MOSSES AND FERNS 



CHAP. 



later showing a division into ventral and dorsal cells. Prob- 
ably this type has been derived from the former by a gradual 
increase in the size of the angle formed by the dorsal and ven- 
tral walls of the apical cell, which finally became so great as 
to practically form one plane. 

The antheridium of Pellia is larger than that of Aneura, 
but its development is very similar except that the stalk is 
multicellular, as it is in the other Anacrogynse. The sperma^ 
tozoids of Pellia (Fig. 40, D, E), are much larger than those 
of Aneura, but are exceeded in size by those of the allied genus 
Makinoa (Miyake (2)). 



\ "\^ 



/ 



/ 







Fig. 4S.—Fossom'bronia longiseta; early stages in the development of the antheridium, 
X525; drawings made by Mr. H. B. Humphrey* D, cross-section. 



In Fossombronia (Fig. 43), which in several respects re- 
calls Sphcerocarpus or Geothallus, the first divisions in the an- 
theridium are median ones, so that in both longitudinal and 
transverse sections the antheridium appears to be divided into 
equal quadrants. The first division, however, is vertical, as it 
is in Aneura. 

The archegonia are borne upon similar but shorter 
branches and their development also is very regular. In Fig. 40, 
B, a vertical section through the end of a young female branch 
is shown with the apical cell {x). Segments are here, too, cut 



Ill 



THE JUNGERMANNIALES 



93 



off alternately right and left, and from each segment an arche- 
gonium develops. The segment is first divided, probahly, as 
in the male branch and the vegetative ones, into an inner and 
an outer cell, but I did not succeed in getting satisfactory longi- 
tudinal sections parallel to the surface, so cannot speak posi- 
tively on this point. The youngest segment, in which the 
archegonium mother cell is recognisable, shows in vertical sec- 
tion three cells, a small ventral one, a middle larger one, anrl 
a dorsal one — the archegonium mother cell. The latter does 
not form any stalk, but divides at once by the three intersect- 
ing walls, as in other Hepatic?e, and the further development 
corresponds with these, except that the base of the archegonium 




B. 





Fig. 44. — Fossomhronia longiscta. Development of the archegonium, longitudinal sec- 
tion, XS25; drawings made by Mr. H. B. Humphrey. 



is not free, and the central cell is below the level of the super- 
ficial cells of the thallus. The archegonium neck is short, and 
the basal part as w^ell as that part of the venter which is free, 
two cells thick (Fig. 40, C). The number of neck cells Is 
small (apparently about four), but whether the number is con- 
stant cannot be stated positively. The female branch remains 



94 MOSSES AND FERNS chap. 

very short, and the archegonia, which are only produced in 
small numbers (usually not more than six to eight), are close 
together and surrounded by an irregular sort of envelope 
formed by the more or less incurved and very much laciniated 
margins of the branch. Secondary hair-like growths are also 
formed, so that to the naked eye the archegonial receptacles 
appear as densely fringed and flattened tufts upon the sides of 
the larger branches. 

The archegonium of Fossombronia (Fig. 44) closely re- 
sembles that of Sphcerocarpus, but it ordinarily has but five 
peripheral rows of neck-cells, as in most of the Jungerman- 
niales. Occasionally, however, there may be six rows, as in 
Sphcerocarpus. 

Janczewski ( i ) followed very carefully the development of 
the archegonium in Pellia epiphylla, which differs a good deal 
from that of Aneura. The archegonia are formed in groups 
just back of the apex, but he does not seem to have been able to 
detect any relation between them and the segments of the 
apical cell such as obtains in Aneura, but it seems probable that 
such a relation does exist. After the archegonium mother 
cell is cut off, it does not at once divide by vertical walls, but 
there is first cut off a pedicel, after which the upper cell under- 
goes the usual divisions. Of the three peripheral cells one is 
much smaller and does not as a rule divide longitudinally, so 
that the neck has normally but five rows of cells instead of six, 
as in the Marchantiacese. Owing to the formation of the 
pedicel, the archegonium is quite free at the base, and like that 
of Aneura the wall of the venter is two-layered. The neck 
becomes very long, and, according to Janczewski, the number 
of neck canal cells may reach sixteen or even eighteen. 

The Sporophyte 

The earliest stages in the embryo are not perfectly known. 
Kienitz-Gerloff (i) investigated Metzgeria furcata and Leit- 
geb ((7), III) species of Aneura. In both of these the first 
division in the embryo separates an upper cell, from which 
capsule and seta develop, from a lower cell, which forms a 
more or less conspicuous appendage at the base of the foot. 
The earliest divisions in the upper part are not known, but it 
soon becomes a cylindrical body consisting of several tier3 of 



in 



THE JUNGERMANNIALES 



95 



cells, each composed of four equal quadrant cells. According 
to Leitgeb (i), the upper tier, from which the capsule develops, 
is formed by the first transverse wall in the up])er part of the 
embryo. This upper tier is next divided by nearly transverse 
walls into four terminal cover cells, and four larger ones below, 
and these latter are again divided each into three cells, an inner 
one and two outer ones, so that the capsule consists of four 
central cells, the archesporium, and twelve wall cells (Fig. 45, 
A). A similar division in the lower tiers results in the forma- 
tion of four axial rows and a single outside layer of cells in 
the stalk. In the lowest tiers the divisions are much less regu- 
lar, and the foot, which is not very largely developed, shows 



A 





Fig. 45.^A, Young embryo of Aneura midtifida, optical section, X235 (after Leit- 
geb); B, median longitudinal section of an older sporogonium of A. pingnis, X35\ 
C, upper part of B, X200; sp, sporogenous cells; el, young elater,s; m, apical group 
of sterile cells. 



no definite arrangement of the cells. The part of the wall of 
the capsule formed from the four cover cells later become two- 
layered, but the rest remains but one cell thick. In Metzgcria 
(Leitgeb (7), III.) the wall becomes later two-layered. The 
archesporium divides first into two layers. In the upper 
cells the divisions are more regular than in the lower one, 
and later the archesporium is made up of cells arranged in 
more or less regular lines, starting from just below the apex 
and radiating from this point, extending to the base of the 
capsule. These cells are at first of similar form, and with 



96 



MOSSES AND FERNS 



CHAP. 




the growth of the capsule become elongated with pointed 
ends that fit together without any spaces between. Some 
of these cells, however, divide rapidly by transverse walls 
and give rise to rows of isodiametric cells (Fig. 45, sp), 
wedged in between others that have remained undivided (el). 

The former are the young 
A . sporogenous cells, the 

latter the elaters. A mass 
of cells lying just below 
the apex, and belonging 
to the archesporium, re- 
mains but little changed, 
and forms the point of 
attachment for the elaters 
after the capsule opens 
(Fig. 45, B, C, m). See 
also Goebel ((21), pp. 

325-327. 

The further develop- 
ment of spores and ela- 
ters is similar to that in 
the higher Marchantia- 
cese, and when the cap- 
sule is mature it opens by 
four valves which extend 
its whole length. '- -^ 

The first division-wall 
in the embryo of Fos- 
sombronia longiseta is 
transverse and divides it 
into two somewhat un- 
equal cells, of which the 

Fig 46.-Fossombronia longiseta. A Section j^^^^^ ^^^ Smaller One 
through a young tetrad of spores; B, surface 

view of the wall of a young spore; C, two givCS risC tO the foOt, and 

young elaters, X6oo; D. two ripe spores; E, ^^^ merely tO the append- 
elaters, X300. -^ ^y 

age of the foot, as is the 
case in Aneiira. From the upper cell arise the seta and the 
capsule. A second transverse wall (Fig. 47, 11.) is formed 
before any longitudinal walls appear. The upper of the three 
cells gives rise, not only to the capsule, but to part of the seta 
as well. The separation of the primary archesporial cells is 





m 



THE JUNGERMANNIALES 



97 



brought about by a periclinal wall in each of the four terminal 
cells, dividing each into an inner archesporial cell, and an 
outer wall-cell. (Fig. 47, D.) 

The capsule wall in Fossomhronia is two cells in thickness, 
except at the apex, where it may be three cells thick. The 
inner layer of cells, when the capsule is ripe, have irregular 
thickened bars developed upon the surface of the radial cell- 
walls. 

The development of the sporogonium is best known in 
Pellia epiphylla (Kienitz-Gerloff (i), Hofmeister (i) ). Here 
the first wall, as in Aneura, separates a lower cell, which sim- 
ply forms an appendage, from the upper cell, from which the 





B. 






Fig. 47. — Fossomhronia longiseta. Development of the embryo, X525; B, E, cross- 
sections; D, shows one of the primary archesporial cells. Figures drawn by 
Mr. H. B. Humphrey. 

stalk and capsule develop. In the latter the first wall is ver- 
tical, and is followed in each of the resulting cells by horizontal 
walls, by which the separation of the capsule from the seta is 
effected. These four cells are now divided by vertical walls, 
so that two layers of four cells each are present. The first 
periclinal walls in the apical group of cells separate the arch- 
esporium from the wall of the capsule. 



98 MOSSES AND FERNS chap. 

The differentiation of the capsule and seta follows as in 
'Aneura, and the arrangement of the cells of the archesporium 
is much the same except that the rows of cells radiate from the 
base of the capsule and not from the summit. The foot is 
very distinct and forms a pointed conical cap, whose edges 
overlap the base of the seta. 

Spore-division in Anacrogynce 

According to Farmer (4), in Pallavicinia decipiens there is 
formed, previous to the division of the nucleus, a "quadripolar" 
nuclear spindle, extending into each of the four lobes of the 
spore mother-cell. Then follows a double division of the 
chromosomes, resulting in sixteen, of which four move to each 
pole of the spindle to form at once the four nuclei of the spore 
tetrad. In Aneura multiUda the formation of a quadripolar 
spindle was also found, but there were subsequently two suc- 
cessive nuclear divisions of the usual type. From his study of 
Pellia epiphylla, Davis (3) has questioned the accuracy of 
Farmer's statements, and Moore's ( i ) studies on Pallavicinia 
Lyalii show that in this species, although a structure which 
might be interpreted as a quadripolar spindle is present, there 
are two successive divisions of the nucleus with bi-polar spin- 
dles. However, the second mitosis follows without an inter- 
vening resting stage of the nucleus. 

The growth of the seta after the spores are ripe is ex- 
tremely rapid, but consists entirely in a simple elongation of 
the cells. Askenasi ( i ) has investigated this in Pellia epi- 
phylla, and states that in three to four days the seta increases 
in length from about i mm. to in some cases as much as 80 
mm., and that this extraordinary extension is at the expense 
of the starch which the outer cells of the young seta contain 
in great abundance, but which disappears completely during 
the elongation of the seta. The growing sporogonium here as 
well as in other species is strongly heliotropic. 

The calyptra in the thallose Anacrogynse is usually massive, 
and in addition there is formed about the growing sporogo- 
nium a special envelope inside the involucre, which in Palla- 
vicinia especially (Fig. 41, A) becomes prolonged into a tube 
which completely encloses the sporogonium until just before its 
dehiscence. 



Ill THE JUNGERMANNIALES 99 

The further development of the spores and elaters corre- 
sponds with that of the Marchantiacea^ (Fig"- 4^), and 
there is the same method of the development of the thicken- 
ings upon the walls of the elaters and the spores. In cases 
where the spores germinate immediately, chlorophyll is devel- 
oped and no proper exospore is formed, although the outer 
layer of the cell wall is more or less cuticularised. 

In the germination of the spores Pcllia offers an exception 
to the other Jungermanniales, in that the spores divide into 
a multicellular body before they are discharged from the cap- 
sule. The presence of centrospheres in the dividing nuclei 
has been demonstrated by Farmer ( 5 ) , and recently Chamber- 
lain (2) has studied these bodies very thoroughly in Pellia. 
The ripe spore here is an oval body which consists of several 
tiers of cells, the end cells being usually undivided, and the 
middle ones each consisting of four equal quadrant cells. 
There is some disagreement as to the earliest stages in the 
germination and the establishment of the apical growth. Hof- 
meister ((i), p. 21) states that in F. epiphylla one end cell 
of the spore grows out into the first rhizoid, while the other 
develops into the growing point of the young plant. Miiller, 
N. J. C. ( ( I ), p. 257), on the other hand, states that in P. caly- 
cina both ends of the spore develop rhizoids while the growing 
point, which at first has a two-sided apical cell, like that of 
Metzgcria, arises laterally. 

The germination of the spores of Aneiira has been studied 
by Kny ( i ) in A. palmata, and by Leitgeb ( (7), III., p. 48) in 
A. pingiiis, which agrees in all respects with the former. The 
spores, as is usual in the Jungermanniales, have a poorly-de- 
veloped exospore, and contain chlorophyll when ripe. Before 
any divisions take place, the spore enlarges to two or three 
times its original volume, and then elongates and by repeated 
cross-walls forms a filament of varying length. In the end 
cell next an inclined wall arises, w^hich is met by another nearly 
at right angles to it, and thus the two-sided apical cell is 
established, and the thallus gradually assumes its complete 
form (Fig. 48, A). 

Connecting the strictly thallose anacrogynous Hepaticas 
with the foliose acrogynous ones, are a number of most in- 
structive intermediate forms. Of these Blasia (Fig. 41, F) is 
perhaps the simplest. Here the margin of the thallus is lobed, 



100 



MOSSES AND FERNS 



CHAP. 



and these lobes, according to Leitgeb's view, are very simple 
leaves. In Fossombronia (Fig. 41, C, D), while the general 
thallose form is more or less evident, the leaves are unmistak- 
able, and as their development shows, morphologically the 
same as the leaves of the acrogynous forms. The most re- 
markable form, however, is Treubia insignis, a very large 
foliose Liverwort discovered by Goebel in Java. This has all 
the appearance of a very large acrogynous form, and also the 

typical three-sided apical 
cell; but in regard to the 
position of the sexual or- 
gans it is typically ana- 
crogynous. These and the 
Haplomitriese form a per- 
fect transition from the 
Anacrogynse to the Acro- 
gynse. 

The multicellular gem- 
mae of Blasia have been al- 
luded to. They are pro- 
duced in long flask-shaped 
receptacles, and when ma- 
ture forrn nearly globular 
brownish bodies whose 
cells contain much oil, and 
whose stalk consists of a 
simple row of cells. Among 
them are glandular hairs, 
which secrete mucilage, by 
the swelling of which the 
gemmae are loosened from 
their pedicels, as in Mar- 
chantia. Similar but sim- 
pler gemmae having usually 
three cells occur in Treubia 
(Goebel (13)). Blasia is also characterised by the presence 
of colonies of Nostoc within the thallus. These occupy cavi- 
ties in the bases of the leaves and are normally always present. 

The Haplomitriece 
The two genera, Haplomitrium and Calobryum, which con- 




B 





Fig. 48. — A, Young plant of Aneura palmata 

X265 (after Leitgeb) ; B, three views of 
a young plant of Pellia calycina, X420 
(Leitgeb). 



m THE JUNGERMANNIALES loi 

stitute this family, differ from all other Ilepaticae in having 
the leaves radially arranged, and not showing the dorsi ventral 
form that characterises all the others. The i)lants are com- 
pletely destitute of rhizoids hut ])ossess a rhizcjme-like basal 
part, from which the leafy axes arise. The latter have well- 
developed leaves arranged more or less distinctly in three rows. 
The stem growls from a tetrahedral ai)ical cell, as in the acrog- 
ynous forms, but in Haploniitriinn at least the apical cell does 
not develop into an archegonium. The archegonia are in this 
genus borne at the end of ordinary shoots, but in Calobrynm 
the end of the female branch becomes much broadened and 
the numerous archegonia stand crowded together. In this 
case it is possible that the apical cell of the stem may finally 
produce an archegonium. Much the same difference is ob- 
servable in the arrangement of the antheridia. 

The Acrogyn^ 

Treuhia and Haplomitrium, as we have seen, connect al- 
most insensibly the anacrogynous with the acrogynous Jun- 
germanniales. The latter are much more numerous than the 
former, but much more constant in form, and are doubtless a 
later specialized group derived from the former. While dif- 
fering in the form and arrangement of the leaves and other 
minor details, they are remarkably constant in their method of 
growth and in the position of the sexual organs, especially 
the archegonia. These are always formed upon special 
branches, where, after a varying number of segments are cut 
off, the apical cell becomes the mother cell of an archegonium. 
The study of any typical form w^ill illustrate the principal 
characters of the group. The species selected, Porella {Ma- 
dotheca) Bolanderi, is very like the common and widely dis- 
tributed P. platyphylla, which corresponds with it in all struct- 
ural points. 

The plant grows upon rocks, especially, but also upon the 
trunks of trees, and forms dense mats closely covering the 
substratum. It branches extensively, but always monopodi- 
ally, dichotomous branching never occurring in the acrogynous 
Jungermanniales. The slender stem is completely hidden 
above by the two row^s of closely-set, overlapping, dorsal 
leaves. Upon the ventral side, which is fastened by scattering 



102 



MOSSES AND FERNS 



CHAP. 



rhizoids to* the substratum, there is a row of much smaller 
leaves (amphigastria), more or less irregularly disposed. The 
dorsal leaves, seen from above, are nearly oval in outline, but 
each has a smaller ventral lobe, pointed at the tip, and closely 
appressed to the lower surface of the much larger dorsal lobe. 
The ventral lobes closely resemble the amphigastria, both in 
form and size, and with the latter form apparently three rows 
of leaves upon the ventral side of the stem. The structure of 
the leaf is of the simplest character, consisting of a single layer 
of polygonal cells containing numerous chloroplasts. 

The plants grow 
where they are exposed 
to alternate wetting and 
drying up. They may at 
any stage become com- 
pletely dried up, and on 
being moistened will re- 
sume at once their ac- 
tivity. In the dried con- 
dition, the species under 
consideration often re- 
mains for several 
months without appa- 
rently being injured in 
the least, and this power 
is shared to a consider- 

FiG. 49.— Porella Bolanderi. A, Female plant, X4; ^^ablc degree by mOSt of 
5, archegonial branches; E, an open sporogo- the aCrOgyUOUS formS, 
nium, X4; C, a male plant, X4; r?> the an- •• ,. ., 1 1 •, , 

theridiai branches. whosc favourite habitat 

is the trunks of trees. 

The apical growth of the stem is extremely regular, and as 
in ail the other acrogynous Hepaticse, the apical cell is a three- 
sided pyramid (Fig. 50, A). In longitudinal section it is 
much deeper than broad, and its outer face is almost flat. In 
cross-sections (Fig. 50, B) it has the form of an isosceles tri- 
angle, the shorter side turned toward the ventral surface of the 
plant. From this cell three sets of lateral segments are cut off, 
two dorsal and one ventral, and "each of these gives rise to a 
row of leaves, a leaf corresponding to each segment of the 
apical cell. The first division wall in each segment is at right 
; angles to its broad faces and divides it into two cells of some- 




.s. 



Ill 



THE JUNGERMANNIALES 



103 



what unequal size. The next wall formed divides the larger 
of the two primary cells into an inner and an outer cell (Fig. 
50, A), so that the young segment now consists of three cells, 
an inner one and two outer ; the latter in the dorsal segments 
correspond to the two lobes usually found in the dorsal leaves. 
The two outer cells now divide by walls in two planes, and 
rapidly grow out above the level of the apical cell and form 







Fig. so. — Porella Bolanderi. A, Median longitudinal section of a vegetative axis; 
B, a cross-section of the apex of a similar one, X500; x, the apical cell; h, hair; 
d, dorsal surface; v, ventral surface; C, male; D, female branch. 

lamellae which remain single-layered, and undergo but little 
further modification beyond an increase in size. From the 
base of the young leaves simple hairs develop, but remain small 
and inconspicuous. The inner of the three first formed cells 
of the segment, by further division and grow^th in all direc- 
tions, produces the axis of the plant. This in cross or longi- 
tudinal section shows almost perfectly uniform tissue. No 
distinct epidermis, or central strand, like that found in most 
Mosses, can be seen. 



I04 MOSSES AND FERNS chap; 

The branching is monopodial and the branch represents 
the ventral lobe of a leaf. After the first division by which 
the two lobes of the leaf are separated, only the dorsal one 
develops into the lamina of the leaf, which is thus in the seg- 
ment from which a branch is to form, only one-lobed. In the 
ventral cell three walls arise (Fig. 51), intersecting so as to 
cut out a pyramidal cell of the same form as the apical cell of 
the main axis, and the cell so formed at once begins to divide 




y. 

Fig. 51. — Diagram showing the ordinary method of branching in the acrogynous Jun- 
germanniaceae (after Leitgeb). D, Dorsal; V, ventral side of stem; X' X", apical 
cells of the branches. The segments are numbered. 

in the same way, and forms a lateral axis of precisely the same 
structure as the main one. 

The genus Physiotium differs from all other known Acrog- 
ynse in having a two-sided apical cell, instead of the typical 
tetrahedral one — (Goebel (21), p. 287). 

The Sex-organs 

The plants in Porella are strictly dioecious and the two sexes 
are at once recognisable. The males are smaller, and bear 
special lateral branches which project nearly at right angles 
from the main axis, and whose closely imbricated light green 



in 



THE JUNGERMANNIALES 



105 



leavei. make them conspicuous. At the base of each of the 
leaves is a long-stalked antheridium, large enough to be readily 
seen with the naked eye. 

The development of the antheridium may be easily traced 
by means of sections made parallel to the surface of the branch. 
At the apex (Fig 50, C) is an apical cell much like that in the 
sterile branches, but with the outer face more convex. The 
divisions in the segments are the same as there, but the whole 
branch remains more slender, and the hairs at the base of the 
leaves are absent. The antheridia arise singly from the bases 




Fig. 52.— P<?f^//o Bolanderi. Successive stages of the young antheridium in median 

longitudinal section, X6oo. 



of the leaves, close to where they join the stem, and are recog- 
nisable in the fourth or fifth youngest leaf (Fig. 50, C, <^). 
The antheridial cell assumes a papillate form, and divides by 
a transverse w^all into an outer and inner cell, and the former 
divides by a similar wall into two cells, of which the upper one 
is the mother cell of the antheridium, and the other the stalk. 
The first wall in the antheridium itself is vertical (Fig. 52, B), 
and divides it into two equal parts. Each of these is now 
divided by two other intersecting walls, best seen in cross-sec- 



io6 



MOSSES AND FERNS 



CHAP. 



tion (Fig. 53, A), which separate a central cell, nearly tetra- 
hedral in form, from two outer cells. In the complete separa- 
tion of the central cell by these first two walls, Porella appears 
to differ from the other Jungermanniacese examined, (Leitgeb 
(7), ii., p. 44), where these first two peripheral cells do not 
reach to the top of the antheridium, and a third cell is cut off 
before the separation of the central part of the antheridium 
from the wall is complete. It is possible, too, that in Porella 
this may be sometimes the case. The antheridium in cross- 
section at this stage shows two perfectly symmetrical halves 





I Vie '., -uL'^ rr\ 'J-, A <\.- ' 





Fig. i^. — -Porella Bolanderi. A, B, Cross-sections of young antheridia, X600; 
C, longitudinal section of nearly ripe antheridium, Xioo; D, ripe antheridium in 
the act of opening, Xso; E, F, spermatozoids, X1200. 



(Fig. 53, A). The two central cells form a rhomboid sur- 
rounded by six cells, the first of the primary peripheral cells 
being in each case divided into two. The divisions proceed 
rapidly in both the central cells and in the peripheral ones. In 
the latter they are for a long time always radial, so that the wall 
remains but one cell thick ; but as the antheridium approaches 
maturity periclinal walls also form in the lower part, which 
thus becomes double, and at places even three cells thick. 
After the division of each primary central cell into equal 



Ill THE JUNGERMANNIALES 107 

quadrants, a series of curved walls intersecting the inner walls 
of the peripheral cells arise, and then periclinal walls (Fig. 
53, 3), but beyond this no definite succession of walls could be 
traced. 

The development of the spermatozoids is the same as in 
other Liverworts. The slender body shows about two com- 
plete coils; the vesicle is small, but always present, and the 
cilia somewhat longer than the body (Fig. 53, F). The stalk 
t)f the antheridium is long and at maturity composed of two 
rows of cells. Before the central cells of the antheridium are 
separated from the peripheral ones, the stalk shows a division 
into two tiers of two cells each (Fig. 52, B), but it is only the 
lower one that forms the real stalk; the other forms the base 
of the antheridium itself. The cells of the walls have numer- 
ous chloroplasts, but the great mass of colourless sperm cells 
within make the ripe antheridium look almost pure white. If 
one of these is brought into water it soon opens in a very char- 
acteristic way. The cells of the wall absorb w^ater W'ith great 
avidity, and finally the upper part bursts open by a number of 
irregular lobes which curl back so strongly that many of the 
marginal cells become completely detached. The whole mass 
of sperm cells, with the included spermatozoids, is forced out 
into the water, and if they are perfectly mature, the spermato- 
zoids are quickly liberated and swnm away (Fig. 53, D.) 

The female plants are decidedly larger than the males, but 
the archegonial branches are much less conspicuous than the 
antheridial ones. The older ones, which either contain a 
young sporgonium or abortive archegonia, are readily distin- 
guished on account of the large perianth (Fig. 49, A), but 
those that contain the young archegonia are situated very near 
the apex of tho main shoot, and are scarcely to be distinguished 
from the very young vegetative branches. However, a plant 
with the older perichgetia, or very young sporogonia, will usu- 
ally show young archegonial branches as wxU. 

The archegonial branch originates in the same way as the 
vegative branches, and the first divisions of its apical cell are 
the same ; but only two or three segments develop leaves, after 
which each young segment divides into an inner and an outer 
cell; the latter becomes at once the mother cell of the young 
archegonium. The inner cell divides further by a transverse 
wall, and the outer of the two cells thus formed gives rise to 



io8 



MOSSES And ferns 



CHAP. 



the short but evident pedicel of the archegonium. The latter 
is very like that of the anacrogynous Liverworts. Of the three 
first walls (Fig. 54, C), the last formed one is much shorter, 
so that one of the three peripheral cells is much smaller, and 
does not divide by a vertical wall, and the neck has but five 
row^s of cells, as in Pellia. This appears to be universal 
among the acrogynous Jungermanniales examined. Often in 
Porella the three primary walls converge at the bottom so as 
to almost meet, in which case the central row of cells is nar- 
rower at the base (Fig. 54, D). The rest of the development 





Fig. z^— 'Porella Bolanderi. Development of the archegonium, X6oo; C, cross-section 
of young archegonium; G, cross-section of the neck of an older one. The others 
are longitudinal sections; b, ventral canal cell; o, the egg. 



is exactly as in the other Hepaticse. The number of neck 
canal cells in the full-grown archegonium is normally eight. 
The archegonium (Fig. 54, F), at maturity is nearly cylin- 
drical, with the venter but little enlarged. The canal cells are 
broad, but the egg small. The venter has a two-layered wall. 
The first-formed archegonia arise in strictly acropetal sue- 



Ill 



THE JUNGERMANNIALES 



log 



cession, and finally the apical cell divides by a transverse wall, 
and the outer cell so formed becomes transformed into an 
archegonium. In a number of cases observed, young arche- 
gonia were noticed among the older ones, apparently formed 
secondarily from superficial cells between them, and not from 
the younger segments of the apical cells. 

A perianth is formed about the group of archegonia, much 
as in the anacrogynous forms. 

Gayet ( i ) has asserted that in the Liverworts, as well as 
in the true Mosses, the growth of the archegonium is largely 
apical. This point has been examined again by the writer 
(Campbell (21)), but Gayet's conclusions were not verified. 




Fig. 55. — Porella Bolanderi. Development of the embryo. A-D, in longitudinal sec- 
tion; E-G, transverse sections. B and C are sections of the same embryo, and 
E, F, G are successive sections of a single embryo, X525. 



The Sporophyte 

The early divisions in the embryo of Porella are less regu- 
lar than those in some others of the foliose Liverworts. The 
embryo at first is composed of a row of cells, of which the 
lowest, cut off by the first transverse wall, undergoes here no 
further development. In Jungermannia bicuspidafa (Hof- 
meister, Kienitz-Gerloff, Leitgeb) this lower cell undergoes 
further divisions to form the filamentous appendage at the base 
of the sporogonium. The next divisions in the upper part of 
the embryo correspond closely to those described in Pellia and 
Aneura, but the succession of the walls is more variable and 



no 



MOSSES AND FERNS 



CHAP. 



the limits of the primary cells more difficult to follow. The 
number of the cells, too, that contribute to the formation of 
the capsule, cannot be determined exactly, and there is evi- 

A. 





ei 




Fig. 56. — Porella Bolanderi. A, Nearly median longitudinal section of an advanced 
embryo, X260; B, the upper part of a similar embryo, X525; C, sporogenous cells 
and elaters from a still older sporogonium, X525. 



dently some variation in this respect, as there is in the time of 
the separation of the capsule wall from the archesporium* 



Ill THE JUNGERMANNIALES in 

Both longitudinal and transverse sections of the sporogonium 
at this stage (Fig. 55, D) show a good deal of irregularity in 
the arrangement of the cells, and the first periclinal walls form 
at very different distances from the surface, so that it is clear 
that the wall cannot be established, as in Radula for instance, 
by the first periclinals. 

The cells of the older archesporium are arranged in more 
or less evident rows radiating from the base (Fig. 56, A). 
No definite relation of spores and elaters can be made out, the 
two sorts of cells being mingled apparently without any regu- 
lar order. Some of the cells cease dividing and grow regu- 
larly in all directions, while others may divide further and 
grow mainly in the plane of division, so that they become 
elongated. The former are the young spore mother cells, the 
latter the elaters (Fig. 56, C). The division of the spores 
begins while the cells of the archesporium are still united, 
although at this time the swollen and strongly striated cell 
walls of the mother cells (Fig. 56, C) show that they are be- 
coming mucilaginous. At this stage sections through the 
archesporium show the deeply-lobed spore mother cells with 
the elongated elaters packed in between them, the pointed ends 
of the latter fitting into the interstices between the spore 
mother cells. The latter are somewhat angular and the wall 
distinctly striated. It is the inner layer only of the wall that 
projects into the cavity of the cell and forms the characteristic 
lobes marking the position of the four spores. The cell cavity 
is filled with crowded granules, some of wdiich are chloroplasts. 
The nucleus, which is of moderate size, and rich in chromatin, 
has a distinct nucleolus. The elaters have thinner walls than 
the spore mother cells, and the contents are more finely granu- 
lar. A distinct nucleus staining strongly with the usual 
reagents is present. The further history of spores and elaters 
corresponds closely with that of the forms already described. 
The ripe spores have only a thin wall, which is coloured brown, 
and has delicate granular thickenings. 

In a paper by Le Clerc du Sablon (3) the statement is 
made, and figures are given, show^ing that at an early stage in 
the development of the spores and elaters of a number of He- 
paticse the walls of the cells are completely destroyed, so that 
the young spore mother cells and elaters are primordial cells. 
A great many carefully stained microtome sections of a large 



112 



MOSSES AND FERNS 



CHAP. 



number of Liverworts belonging to all the principal groups 
have been examined by me, and invariably the presence of a 
definite cell wall could be demonstrated at all stages. 

Many of the foliose Hepaticge show much greater regu- 
larity in the early divisions of the embryo, and in the establish- 
ment of the archesporium and the arrangement of its cells. 
This is especially marked in Frullania (Leitgeb (7), II.). 

Here, after the upper part of 
the embryo has divided into 
three tiers of cells, these under- 
go the usual quadrant divi- 
sions, and the four terminal 
cells only, form the capsule, in 
which the archesporium is es- 
tablished by the first periclinal 
walls (Fig. 58). The divi- 
sions in the archesporium are 
also extremely regular, so that 
the spores and elaters form 
regularly alternating vertical 
rows. In Frullania the lower 
cell of the embryo, instead of 
remaining undivided, or form- 
ing simply a row of cells, di- 
vides repeatedly, and the cells 
grow out into papillae, so that 
it probably is functional as an 
absorbent organ, like the foot 
of the Anthocerotes. Radula 
(Hofmeister (i)) and Junger- 
mannia, while more regular in 
„,,„,,. ^ . the divisions than Porella, still 

Fig. 57. — Porella Bolandert. Longi- . 

tudinai section of a sporogonium after are Icss SO than Frullama, and 

the f^nal division of the archesporial j^ thcSC mOrC than the Upper 

tier of cells take part in the 
growth of the capsule. The degree to which the seta and 
foot are developed varies. In Porella there is not a distinctly 
marked foot, the lower part of the seta being simply somewhat 
enlarged, but in others, like Jungennannia hicuspidata, there 
is a large heart-shaped foot, very distinct from the seta. In 
Porella the seta is short, projecting but little beyond the 




in 



I HE JUNGERMANNIALRS 



113 



perianth; but in others it may reach a length of several centi- 
metres. 

The development of the perianth is quite independent of 
fertilisation, and not infrequently it contains, although fully 
developed, only abortive archegonia. It is not always formed, 
but when present, according to Leitgeb, it is the product of the 
older segments of the apical cell from which archegonia are 
formed, and arises as a sort of wall about the whole group of 
archegonia. In Porella, as well as most of the foliose He- 
paticae, the capsule opens by four equal valves, the lines of 
splitting corresponding, according to Leitgeb, to the first 
quadrant walls in the young embryo. 

The germination of the spores shows a great deal of varia- 
tion, and has been studied in a large number of forms by 
several observers. Recently a number of tropical species have 




Fig. 58. — Frullania dilatata. Development of the embryo, X300 (after Leitgeb); x, x, 
the archesporial cells. The numbers indicate the primary transverse divisions. 



been investigated, especially by Spruce (2) and Goebel (12), 
and some extremely interesting variations have been discov- 
ered. In these forms and when the exospore is not strongly 
developed, it is simply stretched by the expanding endospore, 
and finally becomes no longer discernible ; but when it is clearly 
differentiated, it splits with the swelling of the endospore and 
then remains unchanged at the base of the young plant. The 
germinating spore may give rise to a cell mass immediately, 
which develops insensibly into the leafy axis, or it may form a 
simple or branched protonema of very different form, which 
sometimes reaches a large size and upon which the leafy axis 
arises as a bud. 

The simplest form may be illustrated by Lophocolea, in 
which the germinating spore divides by a transverse wall into 

two equal cells, one of which continues to grow and divide 
8 



114 



MOSSES AMD FERNS 



CHAP. 



until a short filament is formed. After a varying number of 
transverse divisions an oblique wall is formed in the terminal 
cell, and a second one nearly at right angles to it. By these 
divisions the dorsiventral character is established, the first- 
formed segment being ventral. A third oblique wall now 
arises, intersecting both of the others, and the three include a 
tetrahedral cell which is the permanent apical cell of the young 
plant. The ventral segments do not at first form any trace of 
leaf-like structures, and in the dorsal segments the leaves are at 
first simple rows of cells; but a little later the leaves show 
plainly their two-lobed character, each being made up of two 
rows of cells united at the base. From the ventral segments 
the amphigastria develop gradually, being quite absent in the 
earlier ones. Chiloscyphus closely resembles Lophocolea, but 





Fig. 59. — A, Germination of Lejeunia serpyllifolia; B, young plant of Radula com- 
planata; x, the optical cell (all the figures after Goebel). 



the filamentous protonema is longer, and is often branched. A 
similar filamentous protonema is present in Cephalozia (Jun- 
germannia) bicuspidata and other species. 

Lejeunia (Goebel (13) ) shows a most striking resem- 
blance in its early stages to the simple thallose Jungerman- 
niacese. The germinating spore forms either a short filament 
or a cell surface (Fig. 59, A). In either case, at a very early 
stage, a two-sided apical cell is established, and for a time the 
young plant has all the appearance of a young Metsgeria or 
Aneura. This two-sided apical cell gives place to the threes 
sided one found in the older gametophyte, and the leaves and 
stem are gradually developed as in Lophocolea. 

In Radula (Hofmeister (i), p. 55), and according to 



Ill 



THE JUNGERMANNIALES 



"5 



Goebel, much the same condition occurs in Porclla, the first 
divisions of the spore give rise to a disc, and the formation of 
a filament is completely suppressed. This disc is nearly circu- 
lar in outline, and at its edge a single large cell appears (Fig. 
59, B), whose relation to the primary divisions of the spore is 
not quite clear. This cell forms the starting-point for the 




Fig. 6o. — A, Lejeunia metsgeriopsis, showing the thalloid protonema with terminal 
leafy buds (&), X14 (after Goebel). B, Gemma of Cololejeunia Goebelii. 



growing apex of the gametophore. As in the other forms, the 
first leaves are extremely rudimentary, and only gradually is 
the complete gametophyte developed. 

How far this variation in the form of the protonema is of 
morphological importance is a question, as the same species 
may show both a filamentous protonema and the discoid form. 



ii6 MOSSES AND FERNS chap. 

According to Leitgeb this is the case in several species of 
Jungermannia, and he suggests that the conditions under which 
germination takes place probably affect to a considerable extent 
the form of the protonema. This is well known to be the case 
in Ferns. 

The very peculiar modifications observed in certain tropical 
Hepaticae, especially by Spruce and Goebel, should be men- 
tioned in this connection. In these forms the protonema is 
permanent and the leafy gametophore only an appendage to it. 
In Protocephalozia ephemeroides, a species discovered by 
Spruce in Venezuela, the plant forms a dense branching fila- 
mentous protonema much like that of the true Mosses, which it 
further resembles by having a subterranean and an aerial por- 
tion. Upon this confervoid protonema are borne the leafy 
gametophores, which are small and appear simply as buds. 
Among the other remarkable forms is Lejunia metzgeriopsis, a 
Javanese species discovered by Goebel growing upon the leaves 
of various epiphytic Ferns. It has a thallus much like that of 
Metzegeria, and like it has a two-sided apical cell. This thallus 
branches extensively (Fig. 60, A), and propagates itself by 
numerous multicellular gemmae. This thallose condition is, 
however, only maintained during its vegetative existence. 
Previous to the formation of the sexual organs, the two-sided 
apical cell of a branch becomes three-sided, as in the young 
plant of other species of Lejeunia, and from this three-sided 
apical cell a short leafy branch, bearing the sexual organs, is 
produced.^ 

Considerable variety is exhibited by the leaves of the 
Acrogynae as to their form and position, but all agree in their 
essential structure and early growth. The two lobes may be 
either equal in size or unequal. In the latter case either 
the dorsal or ventral lobe may be the larger, when the leaves 
are overlapping, as occurs in most genera. Where the dorsal 
half is the larger it covers the ventral lobe of the leaf in front 
of it, and the leaves are said to be "incubous" ; where the 
reverse is the case, the leaves are ''succubous." These dififer- 
ences are of some importance in classification. 

In many species, especially the tropical epiphytic forms, one 
lobe of the leaf frequently forms a sac-like organ, which ap- 

^ For a complete account of these forms as well as others, see Goebel's 
papers in the Annals of the Buitenzorg Botanical Garden, vols. vii. and ix., 
and in Flora, 1889 and 1893 



in 



THE JUNGERMANNIALES 



117 



pears to serve as a reservoir for moisture. These tubular 
structures sometimes have the opening provided with valves, 
which open readily inward, but not from the inside, and thus 
securely entrap small insects and crustaceans which find their 
way into them. Schiffner ( (i), p. 65) compares them to the 
pitchers of a Sarraccnia or Darlingtonia, and suggests that 
they may serve the same purpose. 

The branching of the foliose Jungermanniaceae has been 
carefully investigated by Leitgeb, and will briefly be stated 
here. Two distinct forms are present, terminal branching 
and intercalary. The former 
has already been referred to, 
but it shows some variations 
that may be noted. In most 
cases the whole of the ventral 
part of a segment, which or- 
dinarily would produce the 
ventral lobe of a leaf, forms 
the rudiment of the branch, 
so that the leaf, in whose axil 
the branch stands, has only 
the dorsal lobe developed. In 
the other case, only a part of 
the cell is devoted to forming 
the branch, and the rest forms 
a diminished but evident 
ventral leaf-lobe, in 
axil the young branch is situ- 
ated. The formation of the 
intercalary branches, which 
are for the most part of endogenous origin, may be illustrated 
by Mastigohryum, wdiere the characteristic flagellate branches 
arise in this manner. The apical cell of the future branch 
(the branches in this case arise in strictly acropetal order) 
springs from the ventral segment, and exactly in the middle. 
It is distinguished by its large size, and is covered by a single 
layer of cells (Fig. 61). In this cell the first divisions estab- 
lish the apical cell, wdiich then grows in the usual way. The 
young bud early separates at the apex from the overlying cells, 
which rapidly grow, and form a dome-shaped sheath, between 




I „„p Fig. 61. — Mastigobryum trilobatum. Longi- 
tudinal section of the stem, showing 
the endogenous origin of the branches; 
X, the apical cell of the branch, X24S 
(after Leitgeb). 



ii8 



MOSSES AND FERNS 



CHAP, 



which and the bud there is a space of some size. Later the 
young branch grows more rapidly than the sheath and breaks 
through it. 

The non-sexual reproduction of the acrogynous Hepatlcse 
may be brought about either by the separation of ordinary 
branches through the dying away of the older parts of the 
stem, or in a few cases observed (Schiffner (i), p. 67) new 
plants may arise directly from almost any point of a leaf or 

stem. Gemmae are known in a 
large number of species. These 
in most of the better known 
cases are very simple unicellular 
or bicellular buds arising often 
in great numbers, especially 
from the margins and apices of 
leaves. Curious discoid multi- 
cellular gemmse have been dis- 
covered in a number of species, 
especially in several tropical ones 
investigated by Goebel (16). 
Gemmae upon the thallus of Le- 
jeunia metzgeriopsis are of this 
character, and similar ones are 
found in Cololejeunia Goehelii. 
In the latter (Fig. 60, B) the 
gemma is a nearly circular cell 
plate attached to the surface of 

Fig. 62.-A, Lejeunia sp.. showing the , . . , ., romnosed of 

ventral leaves, or amphigastria, am ^UC ICai Dy a SldlK COmpOSeU UI 

(X about 40). B, a West Indian a siugle CCll. The first Wall IH 
Lejeunia, the lower leaf-lobes. X, ,1 j* • 1 '^ 

modified as water-sacs (X7S). fhc yOUUg gemma dlVldcS ^it 

into two nearly equal cells, in 
each of which a two-sided apical cell is formed, so that like the 
gemma of Marchantia there are two growing points. There 
are usually four cells that differ from the others in their thicker 
walls and projecting on either side of the gemma above the 
level of' the other cells. These serve as organs of attachment, 
perhaps by the secretion of mucilage, and by them the young 
plant adheres to the surface of the fern leaf upon which it 
grows. The development of the gemmae, whether unicellular 
or multicellular, resembles very closely that of the germinating 
spores. 




.ani 



Ill 



THE JUNGERMANNIALES 



119 



Representatives of the Acrogynae are found in all parts of 
the world, and many of the larger genera are cosmopolitan. 
It is in the wet mountain forests of tropical and subtrcjpical 
regions that they reach their greatest development, both as 
to size and numbers. In these regions they replace to a great 
extent the Mosses of the more northern forests. Some of 
them are extremely minute, and grow as epiphytes upon the 
leaves and twigs of trees and shrubs, or even upon the leaves 
of ferns, or of larger Liverworts. Some of the larger forms, 
like species of Bazzania or Schistochila (Fig. 63) are conspicu- 
ous and characteristic plants. 



Classification of the Acrogynce 

In attempting to subdivide 
this very large family, numer- 
ous difficulties are encountered. 
Their affinity with the Ana- 
crogynse is unmistakable, but it 
is highly improbable that the 
family, as a whole, has had a 
common origin. It is much 
more likely that different types 
of leafy Liverworts have origi- 
nated quite independently from 
different anacrogynous proto- 




FiG. e^.—Schistochiia appendicuiata. A, typcs. While the Acrogynae 



plant of the natural size; B, two show 3. good deal of Variation, 

dorsal and one ventral leaf (v), X2. ,, .-rr . , , 

the dirierences are not constant, 
and the different groups or sub-families merge so into each 
other as to make a satisfactory division of the family almost 
hopeless. According to Schiffner ( i ) , the only one of the sub- 
families which he recognizes, which is clearly delimited, is 
the Jubuloideae. He recognizes the following sub-families 
(Schiffner (i), p. 74) : 

I, Epigonianthese ; II,Trigonanthe3e; III, Ptilidioideae; 
IV, Scapanioidese ; V, Stepaninoidese ; VI, Pleurozioideae; 
VII, Bellincinioidese; VIII, Jubuloideae. 



CHAPTER IV 

THE ANTHOCEROTES 

This group contains but three genera, Anthoceros, Dendro- 
ceros, and Notothylas, and differs in so many essential particu- 
lars from the other Hepaticse that it may be questioned whether 
it should not be taken out of the Hepaticse entirely and given 
a place intermediate between them and the Pteridophytes. All 
the members of the class correspond closely in the structure 
of the gametophyte, and while showing a considerable varia- 
tion in the complexity of the sporophyte, there is a perfect series 
from the lowest to the highest in regard to the degree of de- 
velopment of the latter, so that the limits of the genera, are 
sometimes difficult to determine. The Anthocerotes are of 
extraordinary interest morphologically, as they connect the 
lower Hepaticae on the one hand with the Mosses, and on the 
other with the vascular plants. Leitgeb ( (7), v., p. 9) has en- 
deavoured to show that they are sufficiently near to the Jun- 
germanniales to warrant placing them in a series with that 
order opposed to the Marchantiales, but a careful study of 
both the gametophyte and the sporophyte has convinced me 
that this view cannot be maintained; and that while probably 
the affinities of the Anthocerotes are with the anacrogynous 
Jungermanniales rather than with the Marchantiales, never- 
theless the two latter orders are much nearer each other than 
the former is to either of them. 

The gametophyte in all the forms is a very simple thallus, 
either with or without a definite midrib. Of the three genera 
Dendroceros is confined to the tropical regions, while the other 
genera occur in the temperate zones, but are more abundant in 
the warmer regions, where they also reach a greater size. The 
species of Anthoceros and Notothylas grow principally upon 

120 



IV. THE ANTIIOCEROTES 121 

the ground in shady and moist places, and are usually not 
well adapted to resist dryness. 

The chloroplasts in the Anthocerotacese resemble those in 
certain confervoid Algie, e. g., Stigcoclonium, Colcocliccte. 
Each cell in most species shows a single large chloroplast con- 
taining a pyrenoid. In sterile specimens of an undetermined 
species of Anthoccros from Jamaica, two chloroplasts were 
found in each cell, and a doubling of the chloroplast is not un- 
common in the more elongated thallus-cells of other species, 
while in the sporophyte there seem to be regularly two chloro- 
plasts in each cell. Simple thin-walled rhizoids are formed 
abundantly upon the ventral surface, where there are in many 
species curious stoma-like clefts which open into cavities filled 
with a mucilaginous secretion, and in some of which, in all 
species yet examined, are found colonies of Nostoc which form 
dark blue-green roundish masses, often large enough to be 
readily detected with the naked eye, and which were formerly 
(Hofmeister (i), p. 18) supposed to be gemmae. 

The sexual organs are very different from those of the 
true Hepaticae, and are more or less completely sunk in the 
thallus from the first. While the first divisions in the 
archegonium are much like those in the Hepaticae, the subse- 
quent ones are much less regular except in the axial row of 
cells, and the limits of the outer neck-cells are in the subsequent 
stages difficult to determine, and the archegonium projects 
very little above the surface of the thallus, even when full 
grown. The divisions in the axial row of cells correspond to 
those in the other Archegoniatae. 

The origin of the antheridium is entirely different from 
that of all other Bryophytes, but shows, as will be seen later, 
certain suggestive resemblances to that of the lower Pteri- 
dophytes. Instead of arising from a superficial cell, as in all 
of the former, the antheridium, or in most cases the group of 
antheridia, is formed from the inner of two cells arising by the 
division of a superficial one. The outer one takes no part in 
the formation of the antheridia, but simply constitutes part of 
the outer wall of the cavity in which they develop. 

While the gametophyte is extremely simple in structure, 
being no more complicated than that of Aneiira or Metzgeria, 
the sporophyte reaches a high degree of complexity. Here, 
instead of the greater part of the sporophyte being devoted to 



122 MOSSES AND FERNS chap. 

Spore formation, and dying as soon as the spores are scattered, 
the archesporium, especially in the higher forms, constitutes 
but a small part of the sporogonium, which develops a highly 
dififei entiated system of assimilating tissue, with complete 
stomata of the same type as those found in vascular plants; 
and in addition a central columella is present whose origin and 
structure point to it as possibly a rudimentary vascular bundle. 
In all of them this growth of the sporophyte is not concluded 
with the ripening of the first spores, but for a longer or shorter 
time it continues to grow and produce new spores. This reaches 
its maximum in some species of Antkoceros, where the sporogo- 
nium may reach a length of several centimetres, and continues 
to grow as long as the gametophyte remains alive. In these 
forms the foot is provided with root-like processes, which are 
closely connected with the cells of the gametophyte, from 
which nourishment is supplied to the growing sporophyte. 

The archesporium produces spores and elaters, but the 
latter are not so perfect as in most of the Hepaticas. They 
often show a definite position with regard to the spore mother 
cells; this is especially marked in Notothylas. The arche- 
sporium in all forms that have been completely investigated 
arises secondarily from the outer cells of the capsule. Leitgeb's 
( (7), V. p. 49) conjecture that in Notothylas the whole central 
part of the capsule is to be looked upon as the archesporium, is 
not confirmed by my observations on A^. valvata (orbicularis), 
where the formation of a columella and the secondary develop- 
ment of the archesporium are exactly as in Antkoceros} It is 
hardly likely that in the other species there should be so essen- 
tial a difference as would be implied by such an assumption. 
The development of the spores and their germination show 
some peculiarities which will be considered when treating of 
these specially. The sporogonium shows no clear separation 
into seta and capsule, all except the foot and a very narrow 
zone above it producing spores. At maturity it opens longi- 
tudinally by two equal valves, between which the columella 
persists. The splitting is gradual and progresses with the 
ripening of the spores. 

The genus Antkoceros includes about twenty species, 
widely distributed, but most abundant in the warmer parts of 

^ See also Mottier (2). 



IV. THE ANTHOCEROTES l2Z 

the world. The species that has been most frequently studied 
is A. Iccvis. The related A. Pcarsoni has been carefully in- 
vestigated by the writer, and also the larger A. fiisiformis, a 
common Calif ornian species allied to A. pimctatiis. 

The gametophyte in all species is a dark green or yellowish 
green fleshy thallus, branching dichotomously so that it may 
form orbicular discs not unlike those of the Marchantiaceae in 
shape; but owing to the rapid division of the growing point, 
and the irregular margin of the thallus, the separate growing 
points are not readily made out. The surface of the thallus 
may be smooth as in^. lcsvis,ovmviQh roughened, with ridges 
and spines as in A. fiisiformis. The thallus may be quite com- 
pact, or there may be large intercellular spaces or chambers. 
The latter are not filled with air, as in the similar chambers of 
the Marchantiaceae, but with a soft mucilage. Here and there, 
imbedded in the thallus, are small dark blue-green specks, 
which a closer examination shows to be colonies of Nostoc, 
which are invariably found in the thallus. Colourless rhizoids 
fasten the thallus to the ground. Sometimes the yellowish 
antheridia can be detected with the naked eye, but there is no 
indication visible of the archegonia, which are very inconspic- 
uous and completely sunk in the thallus, and their presence can 
only be detected by sectioning. 

The sporophytes are relatively large and may be produced 
in great numbers, this being especially conspicuous in A. 
fiisiformis, where they may reach a length of six or seven 
centimetres, and- stand so close together that a patch of fruit- 
ing plants looks like a tuft of fine grass. 

Both of the common Calif ornian species, A. Pearsoni and 
A. fusiformis are perennial. The growing point of the shoot, 
with a certain amount of the adjacent tissue, remains alive and 
persists through the summer, after the rest of the plant has 
dried up. Probably the great amount of mucilage in the 
thallus helps to check the loss of water, and enables the plant 
to survive the long summer drought. 

Growth begins promptly with the first autumn rains, and 
by mid-winter, or sometimes earlier, the reproductive organs 
mature. The sporophyte continues to grow in length as long 
as the thallus receives the necessary moisture. New sporog- 
enous tissues develops at the base of the sporophyte long after 
the first spores have been shed. With the cessation of its 



IV. THE ANTHOCEROTES 125 

water-supply through the drying up of the thallus, the sporo- 
phyte finahy dies. 

In order to study the apical growth satisfactorily, young 
plants that show no signs of the sporogonia should be selected. 
In A. fusiformis such a plant will show the margin of the 
thallus occupied by numerous growing points separated by a 
greater or smaller numljer of intervening cells. It is some- 
what difficult to determine positively whether one or more 
apical cells are present. In sections parallel to the surface the 
initial cells are seen to occupy the bottom of a shallow depres- 
sion (Fig. 65, C). In the case figured, x probably is the single 
apical cell, and it seems likely that this is usually the case, al- 
though Leitgeb was inclined to think that there were several 
marginal cells of equal rank. The outer wall of the cells 
shows a very marked cuticle. A vertical section passing 
through one of the growing points (Fig. 66) shows that the 
apical cell is much larger than appears from the horizontal 
section. On comparing the two sections it is evident that its 
form is the same as in the Marchantiaceae or Pallavicinia. Two 
sets of lateral segments, and two sets of inner ones, alternately 
ventral and dorsal, are cut off, and the further divisions of 
these show great regularity, this being especially the case in 
the dorsal and ventral segments. Each of these first divides 
into an inner and an outer cell. The former divides repeatedly 
and in both segments forms the central part of the thallus. It 
is these cells that, according to Leitgeb, later show thickenings 
upon their walls somewhat like those met wdth in many Mar- 
chantiacese. From the outer cells are developed the special 
superficial organs both on the ventral and dorsal sides. From 
the former arise the colourless delicate rhizoids and peculiar 
stoma-like organs, the mucilage clefts, first described by 
Janczewski (i), w^ho also pointed out- the true nature of the 
Nostoc colonies found w^ithin the thallus. These mucilage 
clefts, especially in their earlier stages, resemble closely the 
stomata of the higher plants. They arise by the partial sep- 
aration of two adjacent surface cells close to the growing 
point, and often at least, the two cells bounding the cleft are 
sister cells. However, the same division of the neighboring 
cells frequently occurs without the formation of a cleft, and 
there is nothing to distinguish the two cells bounding the cleft 
from the adjacent ones, and a homology with the real stomata 



126 



MOSSES AND FERNS 



CHAP. 



on the sporogonia is not to be assumed. The mucilage slit 
becomes wider, and beneath it an intercellular space is formed 
which widens into a cavity whose cells secrete the abundant 





Fig. 6s.—~Anthoceros fusiformis. A, Young plant with single growing point {x), X85; 
B, horizontal section of the growing point of a similar plant, XS25; x, the single 
apical cell; C, similar section of a growing point from an older plant, with pos- 
sibly more than one initial cell, X260; D, a mucilage slit from the ventral side of 
the thallus, X525. 



mucilage filling it. This mucilage escapes through the clefts 
and covers the growing point in the same way as that secreted 
by the glandular hairs in the Jungermanniacese. 






n ^ 




^ <: 




o 




♦J 




^S 




u 




O T3 




& X> 




CO 




3 -J 








o'i 




.. 3 




.2 3 




c ^ 




o 




bed 




che 
lise 




U '.^ 




rt t: 




^'H 




c 




3 u 




O J5 




►. •- 




« ^ 








• * <-• 




'"^ -S 




Of rt 




"^ ti 




c 




rt O 




— y 




C 




as 




O 3 




« 5 




u p 




<a bo 




u 




be J3 




C <J 




— u 




^ rt 




o _ 




•gw 




^M . •, 




•S s 




2 3 




o.-^ 




c 




bo o 




S bO 








o o 




U b 




t£ rt 










** a 




««- o 




o 








C Q 




o 








'%S 




ij -^ 




Vi w 




^ u 








"rt u 




.y « 




^C > 




U O 




O o 




> « 




. J3 




< " 




■«"■ 


o 
o 


s ■« 




s .- 


X 


ium 


c 


5 = 


*•«-» 




2^ 


CO 


2 « 




^ o. 


3 


S 'u 


■4-* 


1 >> 


Si 
a 


1 -z 


^ 




c 


o 




M 




P^ 





128 MOSSES AND FERNS chap. 

Each cell of the thallus contains a single chloroplast which 
may be either globular or spindle-shaped, or more or less 
flattened. The nucleus of the cell lies in close contact with 
the chloroplast, and usually partly or completely surrounded 
by it. There is no separation of the tissues into assimilative 
and chlorophylless, as in the Marchantiacese, and in this respect 
Anthoceros approaches the simplest Jungermanniacese, as it 
does in the complete absence of ventral scales or appendages 
of any kind, except the rhizoids. 

The infection of the plant with the Nostoc has been care- 
fully studied by Janczewski and Leitgeb ((7), v., p. 15). The 
infection takes place while the plant is young, and is usually 
brought about by a free active filament of Nostoc making its 
way into the intercellular space below the mucilage slit, through 
whose opening it creeps. Once established, the filament 
quickly multiplies until it forms a globular colony. The 
presence of the parasite causes an increased growth in the cells 
about the cavity in which it lies, and these cells grow out into 
tubular filaments which ramify through the mass of filaments, 
and becomes so interwoven and grown together that sections 
through the mass present the appearance of a loose par- 
enchyma, with the Nostoc filaments occupying the interstices. 
Other organisms, especially diatoms and Oscillarece, often 
make their way into the slime cavities, but according to Leit- 
geb's investigations their presence has no effect upon the 
growth of the thallus. 

Sexual Organs. 

The plants are monoecious in A. fusiformis, and this is 
true of other species observed. In the former, however, the 
antheridia appear a good deal earlier than the archegonia. I 
observed them first on young plants grown from the spores, 
that were not more than 3 mm. in length. The exact origin 
of the cell which the antheridia develops could not be made 
out, as none of my sections showed the youngest stages. 
Waldner's (2) observations upon A. Icevis, however, and my 
own on A. Pearsoni and Notothylas valvata, as well as a study 
of the older stages in A. fusiformis, leave no doubt that in this 
species as in the others the antheridia are endogenous, and the 
whole group of them can be traced back to a single cell. They 
arise close to the growing point, and the cell from which they 



IV. 



THE ANTHOCEROTES 



i2g 



arise is the inner of two cells formed by a transverse wall in a 
surface cell. The outer cell (see Figure 67, 1>) divides almost 
immediately by another wall parallel with the lirst, S(j that the 
group of antheridia is separated by two layers of cells from 
the surface of the thallus. The inner cell in A. Pcarsoni at 
once develops into an antheridium ; but in most species the 
cell divides first by a longitudinal wall into two, each of which 




Fig. 67. — Anthoceros Pearsoni. Development of the antheridium: A, apex of the 
thallus, with very young antheridium, X about 500; B, a somewliat older stage; 
C, still older stage, somewhat less highly magnified; D, an older, but still im- 
mature antheridium, X about 200. 



generally divides again, so that there are four antheridium 
mother cells, all, how^ever, unmistakably the product of a single 
cell, and if a comparison is to be made with the antheridium of 
any other Liverwort, the antheridium in the latter is homol- 
ogous, not with the single one of Anthoceros, but with the 
whole group, plus the two-layered upper wall of the cavity in 
which they lie. 

The first divisions in the antheridium are the same as those 
in the original cell, i.e., the young antheridium is divided longi- 
tudinally by two intersecting walls, and the separation of the 
9 



I30 



MOSSES AND FERNS 



CHAP. 



stalk from the upper part is secondary; indeed in the earhest 
stages it is difficult to tell whether these longitudinal divisions 
will result in four vSeparate antheridia or are the first division 
walls in a single one. Secondary antheridia arise later by 
budding from the base of the older ones, so that in the more 
advanced conditions the antheridial group consists of a varying 
number, in very different stages of development (Fig. 68, A). 

A /->^.--<^>N C, 






I D 







Fig. 68. — Anthoceros fusiformis. Development of the antheridium ; D, E, drawn from 
living specimens, the others microtome sections; D, i, shows the single chloroplast 
in each of the wall cells, and the secondary antheridium {s) budding out from 
its base; 2 is an optical section of the same; E, surface view of full-grown antherid- 
ium; F, cross-section of a younger one. Figs. A, E X225, the others X4S0. 



After the first transverse walls by which the stalk is separated, 
the next division in each of the upper cells is parallel to it, so 
that the body of the antheridium is composed of nearly equal 
octant cells. Then by a periclinal wall each of these eight cells 
is divided into an inner and an outer cell, and the eight central 
ones then give rise to the sperm cells, and the outer ones to 
the wall. The four stalk cells by repeated transverse divisions 
form the four-rowed stalk found in the ripe antheridium. The 
uppermost tier of the stalk has its cells also divided by vertical 
walls and forms the basal part of the antheridium wall. The 
transverse and vertical division walls in the central cells alter- 
nate with great regularity, so that there is little displacement 
of the cells, and up to the time of the separation of the sperm 



IV. THE ANTHOCEROTES 131 

cells the four primary divisions are still plainly discernible, and 
the individual sperm cells are cubical in form. In the per- 
ipheral cells hardly less regularity is observable. Except near 
the apex none but radial walls are formed after the first trans- 
verse v^all has divided the body of the antheridium into two 
tiers, and when complete the wall consists of three well- 
marked transverse rows of cells, the lower being derived from 
the uppermost tier of stalk cells. At the apex the cells are not 
quite so regular (Figs. D, E). In its younger stages the 
antheridium is very transparent and perfectly colourless. In 
each peripheral cell a chloroplast is evident, but at this stage 
it is quite colourless and the nucleus is very easily seen in close 
contact w^ith it. As the antheridium grows the chloroplasts 
develop with it, becoming much larger and elongated in shape, 
and at the same time develop chlorophyll. The mature chloro- 
plast is a flattened plate that nearly covers one side of the cell, 
and its colour has changed from green to a bright orange as in 
the antheridium of many Mosses. The sperm cells are dis- 
charged through an opening formed by the separation of the 
apical cells of the antheridium. These cells do not become 
detached, but return to their original position, so that the 
empty antheridium has its wall apparently intact. The sperma- 
tozoids are small and entirely like those of the other Hepaticse. 

Leitgeb ((7), v., p. 19) found in abnormal cases that the 
antheridia may arise superficially, as in the typical Hepaticse. 
Lampa ( i ) describes a similar exogenous origin for the 
antheridium, but Howe (5) has questioned the accuracy of 
her statements, and thinks that the supposed antheridia were 
tubers, as Frau Lampa's figures do not agree with the structure 
of the typical antheridium. Whether this exogenous developn 
ment of the antheridium is a reversion to a primitive condition 
is impossible to decide, but it is possible that such is the case. 

At first the cell from which the antheridial complex arises 
is not separated from its neighbours by any space. About 
the time that the first divisions in it are formed, the young 
antheridial cells begin to round off and separate from the 
cells above them. With the growth of the surrounding cells 
this is increased, so that before the divisions in the separate 
cells begin, the group of papillate cells is surrounded by a 
cavity of considerable size. To judge by the readiness with 
which the walls of the cavity stain, it is probable that the 



132 MOSSES AND FERNS chap. 

separation of the cells is accompanied by a mucilaginous 
change in their outer layers. 

The first account of the archegonium was given by Hof- 
meister, who, however, overlooked the peripheral cells and only 
saw the axial row. Later Janczewski (2) showed that Antho- 
ceros did not differ essentially in the development of the 
archegonium from the other Hepaticae, and his observations 
were confirmed by the later researches of Leitgeb and Wald- 
ner (2). The formation of archegonia does not begin until 
the older antheridia are mature, and very often, especially in 
A. Pearsoni, few or no antheridia were found on the plants 
with well-developed archegonia. After the formation begins, 
each dorsal segment gives rise to an archegonium, so that they 
are arranged in quite regular rows, in acropetal order. After 
the transverse wall by which the segment is divided into an 
inner and an outer cell is formed, the outer cell becomes at 
once the mother cell of the archegonium, much as in Aneura. 
In this cell next arise three vertical intersecting walls, by 
which a triangular (in cross-section) cell is cut out as in the 
other Hepaticse. Sometimes it looks as if one of these walls 
was suppressed, but even in such cases the triangular form of 
the central cell is evident. The main difference between the 
archegonium at this stage in Anthoceros and the Hepaticse 
lies in the complete submersion of the archegonium rudiment 
in the former. In this respect Aneura, where the base of the 
archegonium is confluent with the cells of the thallus, offers an 
interesting transition between the other Hepaticae, where the 
base of the archegonium is entirely free, and Anthoceros. 

The archegonium rudiment divides into two tiers as in the 
other Liverworts, and the peripheral cells divide longitudinally, 
and the neck shows the six vertical peripheral rows although 
it is completely sunk. Later, the limits of the neck become 
often hard to determine, although by later divisions the central 
cell is surrounded by a pretty definite layer of cells. The 
axial cell divides into two of nearly equal size, but the inner one 
soon increases in breadth more than the upper one. The latter 
divides again by a transverse wall into an outer cell corre- 
sponding to the cover cell of the ordinary hepatic archegonium, 
the other to the primary neck canal cell. The cells of this cen- 
tral row soon become clearly different from the other through 
their more granular contents. The lower cell grows much 



IV. 



THE ANTHOCEROTES 



133 



faster than the others and divides into the Qgg cell and the 
ventral canal cell. The cover cell divides by a vertical wall 
into two nearly equal cells, and these usually, but not always, 
divide again, so that four cells arranged cross-wise form the 
apex of the archegonium. In A. fusiformis in nearly ripe 
archegonia I have sometimes been able to see but two of these 
cover cells, but ordinarily four are present. The neck canal 
cell divides first into two, and these then divide again, so that 
four cells are formed. This was the ordinary number in A. 
fusiformis. In a nearly ripe archegonium of A. Pearsoni five 
neck canal cells were seen, but in no cases so many as 



B. 



C. 






Fig. 69. — Anthoceros fusiformis. A two-celled embryo within the archegonium venter, 
X600; B, C, two longitudinal sections of a four-celled embryo, X600. 

Janczewski describes for A. Icevis, where he says as many as 
twelve may be present. 

If the earlier divisions in the archegonium of Anthoceros 
are compared with those of the other Hepatic^e, the most strik- 
ing difference noticed is the separation of the cover cell. In 
the latter the first division of the axial cell separates the cover 
cell from an inner one, and by the division of the latter the 
primary neck canal cell is cut off from the central cell. In 
Anthoceros the neck canal cell is cut off from the outer, and not 
from the inner cell. 



134 MOSSES AND FERNS chap. 

As the archegonium approaches maturity the cover cells 
become very much distended and project strongly above the 
surrounding cells. In stained microtome sections their walls 
colour very strongly, showing that they have become partially 
mucilaginous. This causes them to separate readily, and they 
are finally thrown off, so that in the open archegonium no trace 
of them is to be seen. The walls of the canal cells and the 
central cell undergo the same mucilaginous change, but here it 
is complete, and before the archegonium opens the partition 
walls of the canal cells completely disappear, and the neck con- 
tains a row of isolated granular masses corresponding in num- 
ber to the canal cells. The ventral canal cell is quite as large 
as the egg, which consequently does not nearly fill the cavity at 
the base of the open archegonium (Fig. 66, D) after the canal 
cells have been expelled. The egg did not, in any sections 
studied, show clearly a definite receptive spot, but appeared to 
consist of uniformly granular cytoplasm with a nucleus of 
moderate size. The upper neck cells in the open archegonium 
become a good deal distended, and the canal leading to the 
egg is unusually wide. Surrounding the central cavity the 
cells are arranged in a pretty definite layer. 

Miss Lyon ((2), p. 288) states that she has frequently 
found archegonia in A. Icevis, produced upon the ventral side 
of the thallus. 

The Sporophyte 

Hofmeister was the first to study the development of the 
embryo in Anthoceros, and described and figured correctly the 
first divisions, but his account of the apical growth, which he 
supposed was due to a single apical cell, and the differentiation 
of the archesporium, was shown by the careful investigation of 
Leitgeb ((7), v.) to be erroneous. The following account 
is based upon a large series of preparations of A. Pearsoni and 
A. fusiformis, which seem to agree in all respects. After 
fecundation the egg at once develops a cellulose wall and be- 
gins to grow until it completely fills the centre cavity of the; 
archegonium. As it grows the uniformly granular appear^, 
ance of the cytoplasm disappears, and large vacuoles a're. 
formed, so that the whole cell appears much more transparent. 
The granular cytoplasm is now mainly aggregated about the 
nucleus, which has also increased in size (Fig. 66, E). The 



IV. THE ANTHOCEROTES I3S 

first division wall is parallel with the axis of the archegonium 
and divides the embryo into two equal parts, in which the 
character of the cells remains much as in the undivided tgg. 
Here too the granules are most abundant about the nucleus, 
from which radiate plates that separate the vacuoles. The 
next divisions are transverse and divide the embryo into two 
upper large cells and two lower smaller ones. The embryo at 
this stage is oval and more or less pointed above. In each of 
the four primary cells vertical walls arise that divide the 
embryo into octants, but the upper octants are decidedly larger 
than the lower. Next, in the upper cells, transverse w^alls are 
formed and the embryo then consists of three tiers of four cells 
each. Of these the cells of the upper tier are decidedly the 
larger. At this stage, in neither species examined by me, 
were any traces present of the projection of the basal cells 
figured by Leitgeb (1. c. PL L). As his drawings w^ere made 
from embryos that had been freed from the thallus, probably 
with the aid of caustic potash, it is quite possible that this ap- 
pearance was due in part at least to the swelling of the cell 
walls through the action of the potash. At any rate in micro- 
tome sections of both species in these early stages, the basal 
cells do not project in the least (Fig. 70, A). The next di- 
visions are very uniform in the upper tier of cells, from which 
the capsule develops, but less so for the two lower ones. In 
the upper tier, seen in cross-section (Fig. 70, B i), a slightly 
curved wall running from the median wall to the periphery 
forms in each quadrant, which thus viewed is divided into an 
inner four-sided and outer three-sided cell. In the former a 
periclinal wall next forms, w^hich cuts off an inner square cell 
(Fig. 70, D). In longitudinal section these periclinal walls 
are seen to be concentric with the outer walls of the cells, and 
to strike the median and quadrant w^alls at some distance below 
the apex of the sporogonium so as to completely enclose the 
central cells (Fig. 70, C). By the formation of these first 
periclinal w^alls the separation of the columella from the wall 
of the capsule is completed, and this is not unlike w-hat obtains 
in the sporogonium of many other Hepaticse; but an essential 
difference must be observed. In the latter the central group 
of cells forms the archesporium ; here these cells, as we shall 
see, take no part in spore formation. In the lower tiers of 
cells similar but less regular divisions occur (Fig. 70, D 2), 



136 



MOSSES AND FERNS 



CHAP. 



and the outer cells begin to grow out into root-like processes 
which push down among the cells of the thallus and obviously 
serve the purposes of haustoria. Leitgeb states that the foot 
arises only from the lowest of the primary tiers of cells, but in 
most of my sections of the earlier stages the fact that the foot 
was composed of two distinct layers of cells, corresponding in 
position to the two lower tiers of cells in the embryo, was very 
obvious (Fig. 70, E). 








Fig. 70. — Anthoceros Pearsoni. Development of the embryo X300; A, C, E, median 
longitudinal sections; B and D, successive cross-sections of embryos of about the 
age of A and C respectively. In E the archesporium is differentiated. 



The origin of the archesporium in Anthoceros was in the 
main correctly shown by Leitgeb, but I find that the extent of' 
the archesporium is less than he represents. In PI. I. Figs. 3 
and 10 of his monograph on the Anthocerotese, he figures the 
archesporium as extending completely to the base of the 
columella. A large number of sections were examined, and 
in no case was this found to be so. Instead, it was only from' 
the cells surrounding the upper half of the columella that the 
archesporium was formed. Previous to the differentiation of) 



IV. . THE ANTHOCEROTES i37 

the archesporium the four primary cells of the columella divide 
by a series of transverse walls until there are about four cells 
in each row. Radial walls also form in the outer cells so that 
their number also increases, and the young capsule consists of 
the central columella composed of four rows of cells and a 
single layer of cells outside. The archesporium now arises 
by a series of periclinal walls in the peripheral cells of the upper 
half only of the capsule, and is thus seen to arise from the 
peripheral cells of the capsule, and not from the central ones. 
Fig. 70, E shows a longitudinal section of the sporogonium at 
this stage. Three parts may be distinguished — the foot, the 
capsule, and an intermediate zone between. The latter is 
important, as it is from this that the meristematic part of the 
older sporogonium is formed. With the separation of the 
archesporium the apical growth ceases, and the future growth 
is intercalary. 

In the capsule cell divisions proceed rapidly in all its parts. 
The original four rows of cells forming the columella increase 
to sixteen, which is the normal number in the fully-developed 
sporogonium. The archesporium, by the formation of a sec- 
ond series of periclinal walls, becomes two-layered, and the 
wall outside the archesporium becomes about four cells thick, 
the outermost layer forming a distinct and well-developed 
epidermis. 

The foot grows rapidly in size, but the divisions are very 
irregular, and finally it forms a large bulbous appendage to the 
base of the sporogonium. The cells are large and the outer 
ones develop still further the root-like character of those in 
the young foot. The tissues of the thallus about the base of 
the sporogonium grow rapidly with it, and the connection 
between the surface cells of the sporogonium foot and the 
adjacent cells of the thallus is very intimate. 

The subsequent growth of the capsule is entirely dependent 
upon the activity of the zone of meristem at its base. This 
divides very actively, and the divisions correspond exactly with 
the primary ones in the young embryo, so that the completed 
portions of the older parts of the capsule are continuous with 
the forming tissues at the base. A series of cross-sections at 
different points, compared with a median longitudinal section, 
shows in a most instructive way the gradual development of the 
different parts of the mature capsule (Fig. y2). The centre 



138 



MOSSES AND FERNS 



CHAP. 



K 



of the sporogonium is occupied by a columella composed of 
sixteen rows of cells, which in cross-section form a nearly per- 
fect square. At the base these cells are thin-walled and show 
no intercellular spaces, but farther up their walls begin to 
thicken and the rows gradually separate until in the upper part 
the columella has somewhat the appearance of a bundle of 
isolated fibres. The archesporium is constantly growing from 
below, and the new cells are cut off from those surrounding the 

columella in the same way as at first. 
The archesporium, as well as the colu- 
mella, can be traced down nearly to the 
base of the capsule, and its cells are very 
early recognisable both by their position 
and by their contents. At first but one 
cell thick, the archesporium soon be- 
comes double, but does not advance be- 
yond this condition. As the archespo- 
rium is followed from the base towards 
the apex of the capsule the cells begin 
to show a differentiation. Up to the 
point where the archesporium becomes 
divided into two layers the cells appear 
alike; but shortly after this their walls 
begin to separate, and two distinct 
forms are recognisable, arranged with 
much regularity in many cases, although 
this arrangement is not invariable. 
Pretty regularly alternating are groups 
of oval, swollen cells, with large nuclei 
and abundant granular cytoplasm, and 
much more slender ones, that may un- 
dergo secondary longitudinal divisions. 
The latter have smaller nuclei and more 
transparent contents. Examination 
higher up shows that the former are 
the spore mother cells, the others the elaters, which here have 
the character of groups of cells, and do not develop the spiral 
thickenings found in most Hepaticse. As these two sorts of 
cells grow older they separate completely, and the spore mother 
cells become perfectly globular. The sterile cells remain more 




Fig. 71. — Anthoceros Pear- 
soni. Median longitudinal 
section through the base 
of the sporogonium. The 
archesporium is shaded. 
F, Foot; V, V, basal 
sheath of calyptra, Xioo. 



IV. 



THE ANTHOCEROTES I39 



or less united, and form a sort of network in whose interstices 
the spores He. 

The development of the spores can be easily lollowed, at 
least in most of the details, in fresh material, and on this 
account it was among the first plants in which cell division was 
studied. The mother cells in all stages can be found in the 
same sporogonium, and on account of their great transparency 
show the process of cell division very satisfactorily. The 
nucleus, however, is small, and its behaviour during the cell 
division is not so easy to follow. The mother cell, just before 
division, is filled with colourless cell sap, and the cytoplasm is 
confined to a thin film lining the cell wall. This cytoplasmic 
layer is somewhat thicker on one side, and here the nucleus is 
situated (Fig. 73, A). Lying close to the nucleus is a round- 
ish body, of granular consistence and yellowish green in colour. 
This is a chloroplast, which at this stage is less deeply col- 
oured than later. The chloroplast contains a number of 
granules, some of which are starch. The cell increases rapidly 
in size, and the nucleus, together with the chloroplast, move 
away from the wall of the cell toward the centre, where they 
are suspended by cytoplasmic threads. The chloroplast next 
divides into two .equal portions, which move apart (Fig. 73, 
B), but remain connected by the cytoplasmic filaments. They 
approach again, and each dividing once more, the four result- 
ing chloroplasts remain close together with the nucleus, in the 
centre of the cell. 

Davis (i) has made a very complete study of the spore 
division in A. IcBvis. In this species the archesporium is less 
massive than in A. Pearsoni or A. fusiformis, and the ar- 
rangement of the sporogenous and sterile cells less regular. 
Davis found that the sporophytic nuclei had regularly eight 
chromosomes, those of the gametophyte four. 

Owing to the small amount of chromatin in the nucleus, 
the karyokinetic figures are small and the changes difficult to 
follow satisfactorily. Enough can be easily made out, how* 
ever, to show that the process is in no way peculiar. There is 
first a nuclear spindle of the ordinary form, and the resulting 
nuclei assume the resting stage before dividing again. Each 
then divides, and the four nuclei move to points equi- 
distant from each other, and which are already occupied by the 
four chloroplasts. After this is accomplished, cell walls arise 



IV. 



THE ANTIIOCEROTES 



141 





simultaneously between the four nuclei dividing the mother cell 
into four tetrahedral cells, — the young spores. The wall of the 
mother cell becomes thicker, and in the later stages swells up 
on being placed in water, so that it interferes a good deal wdth 
the study of the spores in the fresh condition. As the spores 
ripen they develop a thick exospore, which is yellow in colour 
and irregularly thickened in A. Pcarsoni, and in A. fiisiformis 
black and covered wnth small tubercles. The chlorophyll disap- 
pears and the spore becomes filled with oil and other food 
materials. The spores remain together until nearly ripe. The 
elaters, if this name can properly be applied to the sterile cells, 
at maturity consist of 

simple or branching B. "^• 

rows of cells, which in 
some cases arise from 
the division of a single 
one; but more com- 
monly, at least in A. 
Pcarsoni, where they 
branch, it is probable 
that they are to be 
looked upon as merely 
fragments of the more 
or less continuoiis net- 
work of sterile cells. 
The contents mainly 
disappear from the 
older elaters, and their 
walls become thick and 
in colour like the w^all 

of the spores. In A. fiisiformis they are longer and more 
symmetrical than in A. Icuvis, and in one group of the genus, 
according to Gottsche (2), the elaters, which consist of a row 
of five to six cells, have a distinct spiral band as in Dendroccros. 
Leitgeb thinks, however, that this group is more nearly related 
to the latter genus than to Anthoceros proper, inasmuch as in 
addition to the peculiar elaters the epidermis of the capsule has 
no stomata, w^hicli are always present in typical species of 
Anthoceros. 

If the epidermis from the young capsule is examined it is 
spen to be composed of elongated narrow cells much like those 




D 




Fig. 73. — Spore division in A. fusiformis; optical 
sections of living cells, X6oo. 



142 



MOSSES AND FERNS 



CHAP. 



in the epidermis of elongated leaves of Monocotyledons. In 
the older parts some of these cells cease to elongate, and be- 
come more nearly oval (Fig. 75, A). These are the young 
stomata, and exactly as in the vascular plants, each divides 
longitudinally by a septum which later separates in the middle 
and forms the pore surrounded by its two guard cells. The 
walls of the other epidermal cells become much thickened and 
distinctly striated. Each epidermal cell contains two large 
chloroplasts like that in the cells of the gametophyte, and be- 
tween the cells are well-developed air-chambers communicat- 
ing with the stomata, so that there is here a typical assimilative 
system of tissues. 

The doubling of the chloroplast in the cells of the sporophyte 
has been noted by Schimper (A. F. W. Schimper (2)), and 




Fig. 74. — Ripe spores and elaters of A. Pearsoni, X6oo. 



this was observed by the writer in both A. fusiformis and A, 
Pearsoni. 

About the base of the growing sporogonium is a thick 
tubular sheath representing in part the calyptra of the other 
Hepaticse, but involving, besides the archegonium venter, also 
the surrounding tissue of the gametophyte. This sheath keeps 
pace with the growth of the sporophyte for a long time, but 
finally the sporogonium grows more rapidly and projects far 
beyond it, and this remains as a tube surrounding its base. 
The growth of the sporogonium continues as long as the 
gametophyte remains alive, and in A. fusiformis is often 6 



IV. 



THE ANTHOCEROTES 



143 



B 





centimetres or more in length, and reaches nearly this length 
before the first spores are ripe and the capsule opens. This it 
does by splitting at the top into two equal valves between 
which the dried-up columella protrudes. 11ie split deepens as 
the younger spores ripen, and may finally extend nearly to the 
base. It is quite possible, although this point was not investi- 
gated, that the line of dehiscence 
corresponds to the primary verti- 
cal wall in the embryo, as is the 
case in the Jungermanniacese. 

The germination of the 
spores^ has hitherto been ob- 
served only in A. IcBvis. A study 
of the germination in A. fiisi- 
formis shows a general corre- 
spondence with the results of 
other observers, but certain points 
were brought out that do not 
seem to have been observed in 
A. IcEvis. The spores of A. fusi- 
formis are protected by a per- 
fectly opaque black exospore, 
which is covered with small spines or tubercles. These spores 
will not germinate readily when fresh, but after resting for a 
few months grow freely. As in other similar spores, the ex- 
ospore is ruptured along the three ridges upon the ventral side 
{i. e., that with which it was in contact with the other spores 
of the tetrad), and through this cleft the endospore protrudes 
as a papilla which sometimes grows into a very long germ 
tube, or more commonly divides before it reaches a great 
length. Into this tube passes the single chromatophore which, 
during the early period of germination, has resumed its green 
colour, and with it the oil drops and other contents of the 
spore. A good deal of variation was observed here in the 
first divisions, as is the case in A. Icevis. The first division 
wall is, in most cases at least, transverse, and is usually followed 
by a second similar one, before any longitudinal walls appear. 
Then in the end cell two intersecting walls and the formation 
of four terminal quadrant cells are often seen (Fig. yS, D), as 
in other Hepaticae. Variations from this type are often met 

*Hofmeister (i) ; Gronland (i) ; Leitgeb (7), vol. v. p. 29. 



Fig. 7S.— a, Young ; B, fully developed 
stoma from the epidermis of the 
sporogonium oi A. Pearsoni, X250. 



144 



MOSSES AND FERNS 



CHAP. 



with, and some of these are shown in the figures. V^ery 
commonly a second cell is cut off by an oblique wall from the 
germ tube subsequent to the first transverse wall, but this does 
not, at least in the early stages, develop into a rhizoid, the 
first rhizoid being met with only after the young plant has 
become a cell body of considerable size (Fig. yy). 

Whether the young plant regularly grows from a single 
apical cell is difficult to say, but it seems probable, and numerous 
forms like Fig. 76, B were encountered where there certainly 
seemed to be a two-sided apical cell, such as occurs so often in 




Fig. 76. — Antlioceros fusiformis. Germination of the spores, X250. A shows a form 
with very long germ tube; in B there seems to be a definite apical cell; Fig. D, 
2, is an apical view of D, i. 



Other Hepaticse. At a later stage (Fig. 77, B) a single apical 
cell of the form found in the mature thallus is unmistakably 
present. By this time the marginal lobes that give this species 
its peculiar crimped appearance begin to develop. They arise 
close to the growing point, and grow rapidly beyond it, but do 
not show any definite apical growth. The plant at this stage 
has a striking resemblance to the prothallium of Eqiiisetmn. 
With the appearance of the marginal lobes, the first of the 
mucilage slits appears upon the vental surface (Fig. yy), and 
from time to time surface cells grow out into the delicate 



IV. 



THE ANTHOCRROTES 



145 



rhizoids, and a little later the first dichotomy of the growing 
point takes place. Up to this time the young plants appeared 
entirely free from Nostoc, but soon after they were founrl to 
be infected, which no doubt was connected with the formation 
of the mucilage slits through which the Nostoc enters the 
thallus. 

In several species of Anthoccros, especially those inhabiting 
regions with a marked dry season, tubers are devcloj)ed by 
means of which the plants are perennial. Howe (3) finds such 
tubers developed in A. phymatodes, of California, and they are 
found in A. dichotomiis, of Southern Europe, and in A. tiihcr- 





sp 



Fig. 77.-^Anthoceros fusiformis. A, Young plant showing the first rhizoid (r) ; B, 
upper part of an older one with the first mucilage cleft (^0 ; x, the growing 
point, X215. 



osus of Australia (see also Goebel (22), p. 293). The struc- 
ture of these tubers has been studied by Ashworth (i), in 
A. tub er osus. 

Dendroceros 

Dendroceros includes about a dozen species of tropical Liv- 
erworts, which are distinguished at once from Anthoceros by 
the very characteristic form of the thallus. This has a massive 
midrib, projecting below^ but the rest of the thallus is but one 
cell thick and forms lateral wings which are much folded and 
lobed, so that the aspect of the plant is somewhat like a Fossoni- 

hronia. As in Anthoceros, some species have a perfectly com- 
10 



146 MOSSES AND FERNS chap. 

pact thallus without intercelluar spaces (D. cichoraceus) , while 
in others these are very much developed and the thallus has a 
more or less spongy texture, e. g., D. Javanicus. The develop- 
ment of the thallus and sporogonium has been studied by Leit- 
geb ( (7), v., p. 39), and in the main corresponds very closely 
to Anthoceros. A difference may be noted, however, in some 
details. Thus the form of the apical cell is like that of Pellia 
epiphylla, where the inner segments extend the whole depth 
of the thallus, and the division into dorsal and ventral seg- 
ments is secondary. The formation of the wings begins near 
the apex and is the result of the growth of the marginal cells, 
which project strongly and divide rapidly by vertical walls 
only. The walls of the cells are thickened at the angles, and 
the surface view is curiously like a cross-section of the collen- 
chyma of many vascular plants. As in Anthoceros mucilage 
slits are formed, sometimes on both surfaces of the thallus, and 
through these the plant is infected with Nostoc, as in the other 
Anthocerotes. In Dendroceros the Nostoc colonies are very 
large and cause conspicuous swellings upon the thallus. All the 
species of Dendroceros that have yet been examined are monoe- 
cious. 

The antheridia of Dendroceros (Campbell (20)), which 
are larger than those of the other two genera, are developed 
singly in strict acropetal succession, forming a row on each side 
of the midrib. The youngest ones occur very near the apex of 
the shoot. The mother cell arises exactly as in Anthoceros and 
Notothylas, and the periclinal division of the cell lying outside 
it takes place very early, so that almost from the beginning 
there are two layers of cells above the antheridial chamber. In 
all the younger stages met with by the waiter, the antheridium 
lay horizontally nearly parallel wnth the axis of the shoot, and 
was attached to the back of the antheridal chamber, instead of 
at its base, as in the other genera. (Fig. 78, D.) 

The first division in the antheridium is transverse, and sep- 
arates the upper part from the stalk. The next divisions may 
be alike in both of these cells, being vertical walls intersecting 
so as to divide both cells longitudinally into four similar cells. 
In the stalk, however, one of these divisions may be suppressed, 
and in such cases, the stalk has but two rows of cells instead of 
four. In the ripe antheridium the stalk becomes very long, and 
is coiled up in the large antheridial chamber. 



IV. 



THE ANTHOCEROTES 



147 



The archegonium of Dendroceros is much hke that of the 
other genera, perhaps more nearly approaching that of Antho- 
ceros. 

The embryo of Dendroceros resembles more nearly that of 
Anthoceros than it does Notothylas. The archesporium is less 






a. 



D. 




b 



FiC. yZ.— Dendroceros Breutelii. A, Thallus with sporophyte attached, X4; "B, apex 
of the thallus X600; C, archegonium, X600; D, E, young antheridia, X600. 

developed than in either species of Anthoceros that were studied 
by the writer, showing only an imperfect division into two lay- 
ers when seen in section. No stomata are developed in the epi- 



148 



MOSSES AND FERNS 



CHAE. 



dermis of the mature sporophyte, which otherwise cidsel}/ 
resemhles thdit oi Anthoceros. : 

The spores may remain undivided, as in Anthoceros, or in 
some species, e. g., D. crispus, they become multicellular before 
they are discharged. In this respect these species of Dendro- 
ceros recall Conocephalus and Pellia^ where germination begins 
before the spores are set free. 

Notothylas 

The third genus, Notothylas, is of especial interest, because 
it was largely upon the results of his investigations upon this 






Fig. 79. — Dendroceros Breutelii. A, section of young sporophyte, X2S0; B, section of 
mature sporophyte showing spores and elater-like, sterile cells; C, single elater, 
X2S0. 



plant that Leitgeb ( (7), v., p. 39) based his theory of the close 
relationship of the Anthocerotes and Jungermanniales. All 
of Leitgeb's observations on the young capsule were made from 
herbarium material, and, as he himself admits, were in all cases 
embryos that had not fully developed. The writer has made 
a very complete examination of the commonest American spe- 
cies, N. orbicularis (valvata), and the results of the study of the 
development of the sporogonium differ so much from those of 
Leitgeb that they will be given somewhat in detail. Mottier 



IV. 



THE ANTIIOCEROTES 



149 



(2) has also studied this species, and his results agree entirely 
with those of the writer. 

The thallus much resembles a small Antlioccros, and sec- 
tions through it show that in its growth and the development 
and structure of the sexual organs there is close correspondence. 
The thallus contains very large lacunae, which are formed in 
pretty regular acropetal order, and vertical sections show these 
large cavities increasing regularly in size as they recede from 
the apex. Similar but less regular lacunce occur in A. fiisifor- 
mis. The antheridia arise as in AntJwceros, endogenously. 
The youngest stage found is shown in Fig. 80, A. Here evi- 




F\G. 80. — Notothylas orbicularis. Development of the antheridium. D, cross-section, 
the others longitudinal sections; E, nearly ripe antheridium, X300, the other fig- 
ures X600; (^, A, the primary antheridial cells. 



:%'>mrto\'fv''i* ? . jr'vA -f ' -■5.t'jt 



;/^.t5l rj;t 



dently the young antheridia (c?) have been formed by the longi- 
tudinal division of a single hypodermal cell, whose sister epider- 
mal cell has divided again by a transverse wall to form the outer 
wall of the antheridiaT cavity (Figs. A, B). The commonest' 
number of antheridia formed is four.''' "~ r:^':.'^n "■^'^ i 

Less regularity is found in the next divisions than in AnfJio- 
ceros, although in the main they are the same. This is observ- 
able both in longitudinal and cross-sections (see Fig. 80, D). 



150 



MOSSES AND FERNS 



CHAP. 



The full-grown antheridium is more flattened than in either 
species of Anthoceros examined by me, and the stalk shorter 
and thicker, but otherwise closely resembles it, although the 
extremely symmetrical arrangement of the cells, especially of 
the wall, is much less noticeable. 

The archegonia correspond very closely, both in position 
and structure, with those of the other genera, the most marked 
peculiarity being the more nearly equal diameter of the cover 
cell and central cell, and a corresponding increase in the breadth 




Fig. 8i. — Notothylas orbicularis. Development of the archegonium, X6oo; x, 

the apical cell. 



of the neck canal cell. Subsequently the central cell becomes 
much enlarged and the appearance of the fully-developed arche- 
gonium is very much like that of Anthoceros (Fig. 8i, A). 
As in A. fusiformis, the usual number of neck canal cells seems 
to be four, and in no case did the number exceed five. The 
cover cells were four in number in all the archegonia studied, 



IV. 



THE ANTIIOCEROTES 



151 



and are larger than in Anthoccros. As in that genus, they are 
thrown off when the archegonium opens. 

Tlie youngest embryo found was composed of four cells, 
and presented (juite a different appearance from the corre- 
sponding stage in Anthoceros. It is impossible from this stage 
to tell whether the first w^all in the embryo is vertical or trans- 
verse. This embryo consisted of four nearly ecjual quadrants, 
instead of having the two upper cells larger than the lower 
ones. By comparison with the older stages there is little doubt 
that here the first transverse wall separates the foot from the 
capsule, as in Sphccrocarpus^ and that the upper cell develops 
directly into the capsule instead of the latter being determined 
by the second transverse walls. In the next youngest stages 





Fig. Bs.—'Notothylas orbicularis. A, B, Horizontal sections of the growing point with 
young archegonia; C, cross-section of the apex of an archegonium, showing the 
arrangement of the cover cells; D, longitudinal section of a nearly ripe arche- 
gonium, X400. 



found (Fig. 83,6) the archesporium was already differentiated. 
A comparison of this with the corresponding stage of Antho- 
ceros show^s conclusively that the two are practically identical 
in structure. The columella, evidently formed as in AiitJio- 
ceros, and as there made up of four rows of cells, is surrounded 
by the archesporium cut off from the peripheral cells. Leit- 
geb's surmise that the columella is a secondary formation is, 
therefore, for A^. orbicularis at least, entirely erroneous, and it 
is extremely likely that when normal specimens of the other 
species are examined from microtome sections, in the young 



152 



MOSSES AND FERNS 



CHAP. 



stages at least, a similar columella will be found. The single 
embryo that Leitgeb (1. c. PI. IV., Fig. yy) figures of N. orbi- 
cularis (valvata) is at once seen to be abnormal, and as his con- 
clusions were drawn from a study of similar dead embryos in 
the other species, they cannot be accepted without more satis- 
factory evidence. While in the main corresponding to the em- 
bryo of Anthoceros there are some interesting differences which 
are closely associated with the structure of the older sporogo- 
nium. The foot is smaller than in Anthoceros and derived only 
from the lowest tier of cells. The columella is decidely smaller, 
and the archesporium, as well as the young sporogonium wall, 
relatively much thicker. As in Anthoceros, the archesporium 
does not extend to the foot, but is separated by the zone of 



B 






Fig. 83. — Notothylas orbicularis. A, Four-celled embryo; B, C, older embryos, in 
longitudinal section. The archesporial cells are shaded. A, X4S0; B, C, X22S. 



cells which there give rise to the meristem at the base of the 
capsule. The form of the embryo is different too. It is pear- 
shaped and more elongated than in Anthoceros. 

As the embryo develops these differences become more 
apparent and others arise. Fig. 83, C shows a stage where 
the division of the archesporial cells has begun, and it is at once 
apparent how much more conspicuous they are. It is seen too 
that the outer cells of the upper part of the capsule are also 
dividing actively, and that, compared with Anthoceros j the 



IV. THE ANTHOCEROTES 



153 



apical part of the capsule retains its meristematic character for 
a much longer period. Corresponding with this, the growth 
at the base of the capsule is much less marked. The divisions 
in the archesporium are much more active tlian in Anthoccros, 
and the apical part of the capsule retains its meristematic char- 
acter for a much longer period. Corresponding witli tliis, the 
growth- at the base of the capsule is much less marked. The di- 
visions in the archesporium are much more active than in An- 
thoceros, and also less regular. At first divisions occur in the 
upper portion in all directions, so that above the columella there 
is a mass of archesporial tissue much thicker than that below, 
and occupying very much more space than the corresponding 
tissue in Anthoccros. Longitudinal sections through the basal 
part of the older sporogonium show an arrangement of tissues 
similar to those in Anthoccros, but there are differences corre- 
sponding to those in the young stages. The foot (Fig. 84, A) 
is much smaller and flatter, and sometimes shows a very regular 
structure. The central part is composed of a compact mass of 
rather large cells, between which and the base of the capsule is 
a narrow zone of meristematic tissue. The superficial cells do 
not always grow^ out into the root-like processes found in 
Anthoccros and Dcndroccros, but may remain short and project 
but slightly. The cells are characterised by abundant granular 
cytoplasm and conspicuous nuclei, showing that they are prob- 
ably not only absorbent cells, but also elaborate the food mate- 
rials taken in from the gametophyte. The gradual transition 
of the differentiated tissues above into the meristem at the base, 
is precisely as in Anthoccros, and sections at that point in the 
two genera can scarcely be distinguished from one another. 
The columella (in longitudinal section) in both shows four par- 
allel rows of cells, outside of which lies the single row of arche- 
sporial cells, and four rows of cells belonging to the wall of the 
capsule. 

As the section is examined higher up, however, there are 
marked differences, especially in the divisions of the arche- 
sporium. The first divisions in the archesporium of Notothylas 
are periclinal, and for a short distance it is two-layered, as it is 
permanently in Anthoccros ; but still further up it widens very 
rapidly by the formation of repeated periclinal walls, and soon 
comes to be much thicker than either the columella or the capsule 
wall. A further study of the developing archesporium shows 



154 



MOSSES AND FERNS 



CHAP. 



e^ <^ 





J? 


^•^ 




rt 






V 






u 








o 
o 

X 




aj 






J3 


U 




C 






•*^ 


 •> 




(A 

•— < 


o 
o 






CO 






X 




T3 








M 




rt 






(U 


^ 




u 


< 




3 






G 


« 






a 




■M 


rt 

CO 










e 


4) 




3 


J3 






•w 




C 






o 


<*■> 




bo 


O 




o 






t-i 






o 


Fi 




a 
to 


3 

•fH 




<u 


o 




ja 


o. 




-M 


CO 

o 




<+-■ 


JS 




o 


o 

Ui 




lU 


rt 




m 






rt 
J3 


4) 




OJ 






j: 


.^ 




•M 


o 




J3 






hn 


• •. 




3 


O. 




o 


3 




u 






ja 


u 




■*-• 






c 


hn 




o 








J3 










u 






10 


o 

• 1-1 




»— ( 


-M 




rt 


o 




C 


(U 


ro 








T) 




l-H 


3 


a 




bO 


cl 


rn 


G 


CO 


3 


o 




o 


hJ 


J3 


C 

bO 


< 


O 


o 
o 




4-> 


o. 


• 


;-i 


CO 


•s 

Q 


rt 

a 


^ 


s 


pq 




u 




• A 


•** 


CO 

3 


CO 

u 

i) 

■M 




o 




«o 




V 


w 


,__l 




?^ 


rt 


"««* 




o 


llj 


o 


O. 




•kk 


CO 




o 


u 


C3 


^ 


J3 
O 


T) 


1 




B 


Tf 




3 


00 


.rt 


O 




■♦-* 


VJ 






IV. 



THE ANrilOCEROTES 



155 



that the divisions occur with a good deal of regularity. The 
archesporial cells are divided by alternating vertical and trans- 
verse walls into four layers of cells instead of two, as in Antho- 
ceros, and these cells are arranged in regularly placed transverse 
rows. At first the cells appear alike, but later there is a sei)ara- 
tion into sporogenous and sterile cells as in Anthoccros. Mach 
primary transverse row of cells becomes divided into two. The 
upper row grows much faster, and its cells become swollen and 
the cytoplasm more granular, while the lower row has its cells 
remaining flattened and more transparent, i. c, there is a sep- 
aration of the archesporium into alternate layers of sporogenr)us 
and sterile cells as in Anthoceros, but here the 
number of cells is double that in the latter, and 
the longer axis of the cells is transverse instead 
of vertical. In the portion of the archesporium 
above the columella these alternate layers of 
spore mother cells and sterile cells extend com- 
pletely across, and Leitgeb has correctly fig- 
ured this, although he probably was mistaken 
in assuming that this arrangement extended to 
the base of the capsule. 

The further development of the capsule is 
much like that of Anthoceros, but the division 
of the chloroplast takes place before the spore 
mother cells are isolated, and the primary chlo- 
roplast is evident almost as soon as the sporog- 
enous cells are recognisable as such. The 
cells of the columella do not become as elon- 
gated as in Anthoceros, and develop thicken- 
ings much like those of the sterile cells of the 
archesporium; and it was this partly that led 
Leitgeb to the conclusion that even where a 
definite columella was present it probably arose 
as a secondary formation in the archesporium, 
similar to the formation of the axial bundle of 
elaters in Pellia, and that in Notothylas as in 
the Jungermanniales, the archesporium arose 
from the inner of the cells formed by the first 
periclinal w^alls, and not from the outer ones. That this is not 
true for A'', oribictdaris is shown beyond question from sections 
of both the older and younger sporogonium, and it would be 






Fig. 85. — Longitu- 
dinal section of a 
nearly ripe sporo- 
gonium of N. or- 
bicularis, Xso. 



156 MOSSES AND FERNS chap. 

extremely strange if the other species should differ so radically 
from this one as would be the case were Leitgeb's surmise 
correct. 

The wall of the capsule does not develop the assimilative 
apparatus of the Anthoceros capsule, and stomata are com- 
pletely absent from the epidermis. The inner layers of cells 
are more or less completely disorganised, and they probably 
serve to nourish the growing spores, which here, of course, are 
correspondingly more numerous than in Anthoceros. As in the 
latter the sterile cells from a series of irregular chambers in 
which the spores lie. At maturity these sterile cells separate 
into irregular groups. Their walls are marked with short 
curved thickened bands, yellowish in colour like the wall of the 
ripe spores. At maturity the capsule projects but little beyond 
its sheath, and opens by two valves. In some species, e. g., N. 
melanospora, the capsule often opens irregularly. 

The Evolution of the Anthocerotes 

The Anthocerotes form a most interesting series of forms 
among themselves, but are also of the greatest importance in 
the study of the origin of the higher plants. Unquestionably 
Notothylas represents the form which most nearly resembles the 
other Liverworts, but until the other species are investigated 
further we shall have to assume that the type of the sporo- 
gonium is essentially different from that of the lower Hepaticse, 
and corresponds to that of the other Anthocerotes. The pri- 
mary formation of the columella and the subsequent differentia- 
tion of the archesporium occur elsewhere only in the Sphagna- 
cese. From Notothylas, where the archesporium constitutes 
the greater part of the older sporogonium, and the columella 
and wall are relatively small, there is a transition through the 
forms w^th a relatively large columella to Dendroceros, where 
the spore formation is much more subordinated and a massive 
assimilative tissue developed. In Notothylas the secondary 
growth of the capsule at the base, while it continues for some 
time, is checked before the capsule projects much beyond its 
sheath. In Dendroceros the growth continues much longer, 
although it does not continue so long as in Anthoceros. The 
assimilative system of tissue in the latter is finally completed 
by the development of perfect stomata, and the growth of the 



IV. THE ANTIIOCEROTES 



157 



capsule is unlimited. All that is needed to make the sporo- 
phyte entirely independent is a root connecting- it with the 
earth. 

The Inter-rclationships of the Ilcpaticcc 

From a review of the preceding account of the Liverworts, 
it will be apparent that these plants, especially the thai lose 
forms, constitute a very ill-defined group of organisms, f;ne set 
of forms merging into another by almost insensible gradations, 
and this is not only true among themselves, but applies also 
to some extent to their connection with the M(jsses and 
Pteridophytes. The fact that the degree of development of 
gametophyte and sporophyte does not always correspond makes 
it very difficult to determine which forms are to be regarded as 
the most primitive. Thus while Riccia is unquestionably the 
simplest as regards the sporophyte, the gametophyte is very 
much more specialised than that of Aneura or Sphccrocarpus. 
The latter is, perhaps, on the whole the simplest form we know, 
and we can easily see how from similar forms all of the other 
groups may have developed. The frequent recurrence of the 
two-sided apical cell, either as a temporary or permanent con- 
dition in so many forms, makes it probable that the primitive 
form had this type of apical cell. From this hypothetical form, 
in which the thallus w-as either a single layer of cells or with an 
imperfect midrib like Sphcerocarpiis, three lines of development 
may be assumed to have arisen. In one of these the differenti- 
ation was mainly in the tissues of the gametophyte, and the 
sporophyte remained comparatively simple, although showing 
an advance in the more specialised forms. The evolution of 
this type is illustrated in the germinating spores of the Mar- 
chantiacea^, w^here there is a transition from the simple thallus 
with its single apical cell and smooth rhizoids to the complex 
thallus of the mature gametophyte. In its earlier phases it re- 
sembles closely the condition which is permanent in the simpler 
anacrogynous Jungermanniacese, and it seems more probable 
that forms like these are primitive than that they have been de- 
rived by a reduction of the tissues from the more specialised 
thallus of the Marchantiacese. Sphcerocarpiis, showing as it 
does points of affinity wuth both the lower Marchantiales and 
the anacrogynous Jungermanniales, probably represents more 
nearly than any other known form this hypothetical type. Its 



158 MOSSES AND FERNS chap. 

sporogonium, however, simple as it is, is more perfect than 
that of Riccia, and if our hypothesis is correct, the Marchanti- 
ales must have been derived from Sphcurocarpus-likQ forms in 
which the sporophyte was still simpler than that of existing 
species. Assuming that this is correct, the further evolution 
of the Marchantiales is simple enough, and the series of forms 
from the lowest to the highest very complete. 

In the second series, the Jungermanniales, starting with 
Sphcerocarpus, the line leads through Aneura, Pellia, and simi- 
lar simple thallose forms, to several types with more or less 
perfect leaves— ^.^.^ Blasia, Fossombronia, Treuhia, Haplomit- 
rium. These do not constitute a single series, but have evi- 
dently developed independently, and it is quite probable that 
the typical foliose Jungermanniacese are not all to be traced 
back to common ancestors, but have originated at different 
points from several anacrogynous prototypes. 

The systematic position of the Anthocerotes is more diffi- 
cult to determine, and their connection with any other existing 
forms known must be remote. While the structure of the thal- 
lus and sporogonium in Notothylas shows a not very remote 
resemblance to the corresponding structures in Sphcerocarpus, 
it must be remembered that the peculiar chloroplasts of the 
Anthocerotes, as well as the development of the sexual organs, 
are peculiar to the group, and quite different from other Liver- 
worts. To find chloroplasts of similar character, one must go 
to the green Algae, where in many Confervacese very similar 
ones occur. It is quite conceivable that the peculiarities of the 
sexual organs may be explained by supposing that those of 
such a form as Sphcero carpus, for example, should become co- 
herent with the surrounding envelope at a very early stage, and 
remain so until maturity. In Aneura we have seen that the 
base of the archegonium is confluent with the thallus, in which 
respect it offers an approach to the condition found In the An- 
thocerotes; but that this is anything more than an analogy is 
improbable. The origin of the endogenous antheridium must 
at present remain conjectural, but that it is secondary rather 
than primary is quite possible, as we know that occasionally the 
antheridium may originate superficially. In regard to the 
sporogonium, until further evidence is brought forward to 
show^ that Nofothylas may have the columella absent in the early 
stages, it must be assumed that its structure in the Anthocerotes 



IV. THE ANTHOCEROTES i59 

is radically different from that of the other Liverworts. Of the 
lower Hepaticae Sphccrocarpiis perhaps offers again the nearest 
analogy to Notothylas, but it would not be safe at present to 
assume any close connection between the two. Of course the 
very close relationships of the three genera of the Anthocerotes 
among themselves are obvious. 

On the whole, then, the evidence before us seems to indicate 
that the simplest of the existing Hepaticse are the lower thallose 
Jungermanniales, and of these Sphcorocarpiis is probably the 
most primitive. The two lines of the Marchantiales and Jun- 
germanniales have diverged from this common ancestral type 
and developed along different lines. The Anthocerotes cannot 
certainly be referred to this common stock, and differ much 
more radically from eitl:er of the other two lines than these 
do from each other, so that at present the group must be looked, 
upon as at best but remotely connected with the other Hepaticae, 
and both in regard to the thallus and sporophyte has its nearest 
affinities among certain Pteridophytes. The possibility of sep- 
arate origin of the Anthocerotes from Coleochcete-Wke ancestors 
is conceivable, but it seems more probable that they have a com- 
mon origin, very remote, it is true, with the other Liverworts. 
They may probably best be relegated to a separate class, coordi- 
nate with the Hepaticae and Musci. 



CHAPTER V 

THE MOSSES (MUSCI) : SPHAGN ALES— ANDREW ALES 

The Mosses offer a marked contrast to the Hepaticse, for 
while the latter are pre-eminently a generalised group, the 
Mosses with a very few exceptions form one of the most 
sharply defined and specialised groups of plants known to us. 
Although much outnumbering the Liverworts in number of 
species, as well as individuals, the differences in structure be- 
tween the most extreme forms are far less than obtain among 
the Liverworts. While the latter occur as a rule in limited 
numbers, and for the most part where there is abundant 
moisture, the Mosses often cover very large tracts almost to 
the exclusion of other vegetation, especially in northern 
countries. In more temperate regions, the familiar peat-bogs 
are the best known examples of this gregarious habit. Mosses 
are for the most part terrestrial, and are found in almost all 
localities. Some grow upon organic substrata, especially de- 
caying wood, and are to a greater or less extent saprophytic. 
Haberlandt (4) first called attention to this, and investigated 
a number of forms, among them Rhynchosfegium murale, 
Eurynchhtm prcelongum, Wehera nutans, and others, and in 
these found that the rhizoids had the power of penetrating the 
tissue of the substratum, much as a fungus would do. The 
most remarkable case, however, is Buxhaumia, where the 
leaves are almost completely absent and the saprophytic habit 
very strongly pronounced. . Most of the Mosses, however, are 
abundantly provided with assimilative tissue, and grow upon 
almost every substratum, although most of them are pretty 
constant in their habitat. A number of species are typically 

aquatic, e. g., Fontinalis and many species of Sphagnum and 

160 



CH.v. MOSSES (MUSCI): SPHAGN ALES— ANDRE.^ALES i6i 

Hypmim; others grow regularly in very exposed situations on 
rocks, e. g., Andrecea. Very many, like Funaria hygrometrica 
and Atrichmn undiilatiini, grow upon the earth ; and others 
again, like species of Mniiun and Thuidiuni, seem to grow 
exclusively upon the decaying trunks of trees. Indeed Mosses 
are hardly absent from any locality except salt water. With 
the exception of the Sphagnaceae and Andreaeacese, and pos- 
sibly Archidium, the type of structure found among the Mosses 
is extraordinarily constant, and they may all be unhesitatingly 
referred to a single order, the Bryales, which includes within 
it an overwhelming majority of the species. 

The gametophyte of the Musci always shows a well- 
marked protonema, which in most cases has the form of an 
extensively branching alga-like filamentous structure, from 
which later a distinct leafy axis arises as a lateral bud. In 
Sphagnum this protonema is a flat thallus, and the same is true 
of TetrapJiis and a few other forms, but the filamentous proto- 
nema is very much more common. The gametophore arises 
from this protonema as a lateral bud, which develops a 
pyramidal apical cell, from which three sets of segments are 
cut off, each segment producing a leaf. The only exception 
to this, so far as is known at present, is the genus Fissidens 
(Leitgeb (2)), where the apical cell is wedge-shaped, and 
only two sets of segments are formed. Upon these leafy 
branches the sexual organs are borne. The relative degree of 
development of the protonema and the gametophore differ 
much in different forms. Thus in the Phascacese the proto- 
nema is permanent, and the gametophore small and poorly 
developed. In the higher Mosses the protonema disappears 
more or less completely, and the assimilative functions are 
entirely assumed by the large highly developed gametophore, 
which is capable of reproducing itself by direct branching 
without the intervention of the protonema. The commonest 
type of gametophore is the upright stem with the leaves ar- 
ranged radially about it, but in many creeping forms, such as 
some species of Mnhim, Hypmim, etc., the gametophore is 
more or less dorsiventral ; but in these the apical cell is pyram- 
idal, and produces three rows of leaves. Growing out from 
the base of the stem in most Mosses, and fastening it to the 
substratum, are numerous brown rhizoids which are not, how- 
ever, morphologically distinct from the protonema. Thus if 
II 



i62 MOSSES AND FERNS chap. 

a turf of growing Moss is. turned upside down, the rhizoids 
thus exposed to the hght very soon develop chlorophyll, and 
grow out into normal protonemal filaments. 

In most of the Mosses the leaves show a one-layered lamina 
traversed by a midrib, which may be quite small or very 
massive. This midrib is made up in part of elongated thick- 
walled sclerenchyma, and contains a conducting tissue. The 
highest grade of development of the leaf is met with in the 
PolytrichacecEj where the midrib is very massive and peculiar 
vertical laminae of chlorophyll-bearing cells grow out from the 
surface of the leaf. In Bnxbaumia the leaves are almost en- 
tirely abortive. The peculiar leaves of Sphagnum will be re- 
ferred to later, as well as the details of structure of the leaves 
of other forms. 

The stem, except in the lowest forms, is traversed by a 
well-defined central strand of conductive tissue, and in a few 
of the highest ones, e. g. Polytrichum, there are in addition 
smaller bundles, continuations of the midribs of the leaves, 
recalling the "leaf-traces" found in the stems of Spermato- 
phytes. 

The types of non-sexual reproduction among the Musci 
are extraordinarily various, and a careful study of them shows 
that the morphological connection between the protonema and 
gametophore is a very intimate one, as they may arise recip- 
rocally one from the other. With the exception of certain 
resting buds developed from the protonema it appears (Goebel 
(lo), p. 170) that the formation of the leafy stem is always 
preceded by the protonema. The latter arises primarily from 
the germinating spores, but may develop secondarily from 
almost any part of the gametophore or even in exceptional 
cases from the cells of the sporophyte (Pringsheim (2) ; 
Stahl (i)). From these protonemal filaments new gameto- 
phores arise in the usual way. The gametophore itself, es- 
pecially where it is large and long lived, by the separation of 
its branches rapidly increases the number of new individuals. 
This is especially marked in Sphagnum, where this is the 
principal method of propagating the plants. Special organs 
of propagation in the form of gemmse also occur, and these 
may develop from the protonema or from the gametophore 
Tetraphis pellucida (Fig. 118) is a good example, showing 
these specialised gemmse which after a time germinate by 



V. 



MOSSES (MUSCI): SPHAGN ALES— ANDRE/HALES 163 



giving rise to a protonema upon which, as usual, the gameto- 
phore arises as a bud. In size the gametophore of the Mosses 
ranges from a milHmetre or less in height in Biixbaiimia and 
Ephemerum to 30 to 50 cm. in the large Polytrichacese and 
Fontinalis. The branching of the gametophore. is never 
dichotomous, and so far as is known the lateral branches arise, 
not in the axils of the leaves, but below them. Underground 



t , 



C^' 



%v ^' 






/IS 



<i^<^>'- 







Fig. 86. — Climacium Americanum, showing the formation of stolons, Xi» 



Stems or stolons, which afterwards develop into normal leafy 
axes, are common in many forms, e. g., Climacium (Fig. 86). 
The sexual organs are borne either separately or together 
at the summit of the gametophoric branches. Where the 
plants are dioecious, it sometimes happens that the two sexes 
do not grow near together, in which case, although archegonia 



i64 MOSSES AND FERNS CHAP. 

may be plentiful, they fail to be fecundated and thus no cap- 
sules are developed. This no doubt accounts for the extreme 
rarity of the sporogonium in many Mosses, although in other 
cases, e. g., Sphagnum, it would appear that the formation of 
the sexual organs is a rare occurrence. These resemble in gen- 
eral those of the Hepaticse, but differ in some of their details. 
The leaves surrounding them are often somewhat modified, 
and in the case of the male plants (Atrichum, Polytrichum) 
different in form and colour from the other leaves, so that the 
whole structure looks strikingly like a flower. As a rule, the 
archegonial receptacles are not so conspicuous. The early 
divisions of the archegonium correspond closely with those of 
the Liverworts, but after the ''cover cell" is formed, instead 
of dividing by cross walls into four cells, it functions for some 
time as an apical cell, and to its activity is largely due the fur- 
ther development of the neck. The venter is usually very 
much more massive than in the Hepaticse, and the egg small. 

The antheridia, except in Sphagnum, are borne also at the 
apex of the stem, whose apical cell does not always, at any rate, 
become transformed into an antheridium, as we sometimes find, 
especially in species of Atrichum and Polytrichum, that the 
axis grows through the antheridial group and develops a leafy 
axis, which later may form other antheridia at its apex. Where 
the plants are dioecious the males are usually noticeably smaller 
than the females. The antheridia, except in Sphagnum, are 
very uniform in structure, and like the archegonium exhibit a 
very definite apical growth (Fig. 102). The wall remains 
one-layered, as in the Liverworts, and often the chromatophores 
in its cells become red at maturity, as in some Liverworts, e. g., 
Anthoceros. The ripe antheridium is in most Mosses club- 
shaped, and the sperm cells are discharged while still in con- 
nection, the complete isolation of the sperm cells only taking 
place some time after the mass has lain in water. In Sphag- 
num the antheridia are much like those of certain leafy Liver- 
worts, and stand singly in the axils of the leaves of the male 
branches. 

Holferty ( i ) describes and figures a number of interesting 
abnormalities in Mnium cuspidatum in which organs are some- 
times developed which are intermediate in character between 
archegonia and antheridia. 

The sporophyte of the Mosses reaches a high degree of 



V. MOSSES (MUSCI): SPHAGNALES—ANDREJEAl.ES 165 

development in the typical forms, and shows great uniformity, 
both in its development and in the essential structure of the 
full-grown sporophyte. With the exception of Splicr^iiion, 
which will be referred to more specially later, the early growth 
of the sporogonium is due to the segmentation of a two-sided 
apical cell. The separation of the archesporium takes place at 
a late period, and like that of Anthoccros it occupies but a very 
small part of the sporogonium, which in all the liigher forms 
attains a considerable size and comi)lexity. All the archesporial 
cells form spores, and no trace of elaters can be found. 

In all but the lower types, the sporogonium becomes 
differentiated into a stalk (seta) and a capsule. This differ- 
entiation is gradual, and the elongation of the seta is not a 
rapid process, due simply to an elongation of the cells, but is 
caused by actual growth and cell division. In Sphagnum 
and Andrecea, where no seta is present, the axis of the gameto- 
phore elongates and forms a sort of stalk (pseudopodium), 
which carries up the capsule above the leaves. 

The formation of the capsule and seta takes place by a 
rapid enlargement of the upper part of the very much elongated 
embryo about the same time that the archesporium becomes 
recognisable. This enlargement is accompanied by a separa- 
tion of the cells of two layers of the wall, by w^hich an inter- 
cellular space is formed which later may become very large 
(Figs. 109-112). A second similar space may be developed in- 
side the archesporium, but this is found only in the Polytrich- 
aceae. In the Sphagnacese and the Andreseacese this space is 
not developed. These lacunae are traversed by protonema-like 
filaments of chlorophyll-bearing cells, and the cells of the mass- 
ive wall of the capsule also contain much chlorophyll, so that 
there is no question that the sporogonium is capable of assimila- 
tion. Stomata, much like those of AntJwceros or the vascular 
plants, occur upon the basal part of the capsule in many species, 
but are not always present. 

In Sphagnum and all the higher Bryales the capsule opens 
regularly by means of a circular lid or operculum. This in the 
latter group is a most characteristic structure, and with its 
accompanying structures, the "annulus" and "peristome," form 
some of the most important distinguishing marks of different 
genera and species. When ripe, the operculum falls off and 
the ripe spores are set free. The teeth of the peristome, by 



i66 MOSSES AND FERNS chap. 

their hygroscopic movements, play an important part in scat- 
tering the spores, and physiologically take the place of the 
elaters of the Hepaticse. 

Some Mosses live but a few months, and after ripening 
their spores, die. This is the case with Funaria hygrometrica, 
at least in California. Other Mosses are perennial, and some 
species of peat or tufa-forming Mosses seem to have an un- 
limited growth, the lower portions dying and the apices grow^ 
ing on until layers of peat or tufa of great thickness result, 
covered over with the still living plants whose apices are the 
direct continuation of the stems which form the basis of the 
mass. 

With the exception of a very few forms all the Mosses are 
readily referable to three orders. The first two, the Sphagnales 
and the Andreaeales, are represented each by a single genus, and 
are in several respects the types that come nearest the Liver- 
worts. All the other Mosses, except perhaps Archidium and 
Buxhaumia, conform to a very well-marked type of develop- 
ment, and may be referred to a common order, the Bryales. 
The Phascacese or cleistocarpous Mosses are sometimes sep- 
arated from the higher Bryales as a distinct order, but a study 
of their development shows that they belong to the same series, 
and only differ in the degree of development from the more 
specialized stegocarpous forms. 

Order I. — Sphagnales 

The Sphagnales, or Peat-Mosses, are represented by the 
single genus Sphagnum. They are Mosses of large size, 
which, as is well known, often cover large tracts of swampy 
land and about the borders of lakes, forming the familiar peat- 
bogs of northern countries. Owing to the empty cells in the 
leaves and outer layers of the stem, they suck up water like a 
sponge, and the plants when growing are completely saturated 
with water. The colour is usually pale green, but varies much 
in depth of colour, and in many species is red or yellow. When 
dry the colour is much duller, largely owing to the opacity of 
the dry, empty cells which conceal to a great extent the colour 
of the underlying tissues. They branch extensively, and, ac- 
cording to Schimper, a branch is always formed corresponding 
to every fourth leaf ; but Leitgeb has shown that although this 



V. 



MOSSES (MUSCI): SPHAGN ALES— ANDREW ALES 167 



is the rule numerous exceptions to it occur. In sterile plants 
the branches are of two kinds, long flagellate branches which 
hang down almost vertically and are applied to the stem, and 
much shorter ones that are crowded together at the apex and 
have only a limited growth. The leaves are inserted on the 




Fig. B7.^'Sphagnutn (sp); A, B, Young protonemata, X262; C, an older protonema 
with a leafy bud (fe), X about 40; r, marginal rhizoids. 



Stem by a broad base, and taper to a more or less well-marked 
point. According to Schimper, the divergence of the leaves 
of the main axis is always two-fifths, but on the smaller 
branches variations from this sometimes occur. The leaves 



i68 



MOSSES AND FERNS 



CHAP. 



sp 



show no trace of a midrib. As the axis elongates the leaves 
become separated, as well as the lower branches, but upon the 
smaller branches they remain closely imbricated. Rhizoids 
are present only in the earlier stages of the plant's growth, and 
are only occasionally found in a very rudimentary condition in 
the older ones. 

The spores of Sphagnum on germination form first a very 
short filament, which soon, at least when grown upon a solid 
substratum, forms a fiat thallus, which at first sometimes grows 

by a definite apical cell (C. 
Muller (3)). It first has a spatu- 
late shape (Fig. 87, A, B), which 
later becomes broadly heart-shaped, 
and closely resembles in this condi- 
tion a young Fern prothallium, for 
which it is readily mistaken. The 
older ones become more irregular 
and may attain a diameter of sev- 
eral millimetres. The thallus is 
but one cell thick throughout its 
whole extent, and is fastened to the 
earth by colourless rhizoids. Later 
similar filaments grow out from the 
marginal cells of the thallus, and a 
careful examination shows that 
they are septate, and closely re- 
semble the protonemal filaments of 
other Mosses. Like those, the 
Fig. z%. — sphagnum squarrosum. g^p^^ especially in the colourlcss 

Leafy shoot with sporophytes ^ ^ -^ 

(sp), borne at the end of leaf- oues, are strougly obliquc. ihese 
less branches, or "pseudopodia," marginal protoucmal threads may, 

according to Hofmeister (i) and 
Schimper (i), produce a flattened thallus at their extremity, 
and thus the number of fiat thalli may be increased. Schimper 
states that if the germination takes place in water, the forma- 
tion of a fiat thallus is suppressed and the protonema remains 
filamentous, but Goebel disputes this. 

In the few cases observed by me, only one leafy axis arose 
from each thalloid protonema, and although this is not expressly 
stated by Hofmeister and Schimper, their figures would indi- 
cate it. At a point, usually near the base, a protuberance is 




■"^ 



V. 



MOSSES (MUSCI): SPHAGNALES—ANDREALALES 169 



formed by the active division of the cells, in a manner probably 
entirely similar to that in other Mosses, and this rapidly as- 
sumes the form of the young stem. The first leaves are very 
simple in structure, and are composed of perfectly uniform 
elongated quadrilateral cells, all of which contain more or less 
chlorphyll. Like the older ones, however, they show the char- 
acteristic two-fifth divergence. Schimper states that the fifth 
leaf, at the latest, shows the differentiation into chlorophyll- 



A. 







Fig. 89. — Sphagnum cymbifolium. A, Median longitudinal section of a slender branch; 
X, the apical cell; B, part of a section of the same farther down, showing the 
enlarged cells at the bases of the leaves, and the double cortex (cor) ; C, cross- 
section near the apex of a slender branch; D, glandular hair at the base of a 
young leaf — all X525. 



bearing and hyaline cells, found in the perfect leaves. The 
first leaves in which this appears only show it in the lower part 
the cells of the apex remaining uniform. 



170 MOSSES AND FERNS chap. 

At the base of the young plant very deHcate colourless 
rhizoids are developed, and these show the oblique septa so 
general in the rhizoids of other Mosses. As the plant grows 
older these almost completely disappear. 

The apex of the stem and branches is occupied by a pyram- 
idal apical cell with a very strongly convex outer free base. 
From the lateral faces of the apical cell, as in the acrogynous 
Liverworts, three sets of segments are formed. The whole 
vegetative cone is slender, especially in the smaller branches. 
The first division in the young segment is parallel to its outer 
face, and separates it into an inner cell, from which the central 
part of the axis is formed, and an outer cell which produces the 
leaves and cortex. 

The second wall, which is nearly horizontal, divides the 
outer cell of the segment into an upper and a lower cell, the 
former being much broader than the latter, which is mainly 
formed from the kathodic half of the segment, which is higher 
than the anodic half (Leitgeb (i)). The next wall divides 
the upper cell into an upper and a lower one, the former being 
the mother cell of the leaf, the lower, with the other basal cell, 
giving rise to the cortex. Growth proceeds actively in the 
young leaf, which soon projects beyond the surface of the stem, 
and by the formation of cell walls perpendicular to its surface 
forms a laminar projection. The position of the cell walls in 
the young leaf is such that at a very early period a two-sided 
apical cell is established, which continues to function for a long 
time, and to whose regular growth the symmetrical rhomboidal 
form of the cells of the young leaf is largely due (Fig. 90). 
The leaves do not retain their original three-ranked arrange- 
ment, but from the first extend more than one-third of the cir- 
cumference of the stem, S"o that their bases overlap, and the 
leaves become very crowded, and the two-fifth arrangement is 
established. The degree to which the central tissue of the stem 
is developed varies with the thickness of the branch. In the 
main stem it is large, but in the small terminal branches it is 
much less developed, as well as the cortex, which in these small 
branches is but one cell thick. Later the cortex of the large 
branches becomes two-layered (Fig. 89, B), and is clearly sep- 
arated from the central tissue, whose cells in longitudinal sec- 
tion are very much larger. In such sections through the base 



V. MOSSES (MUSCI): SPHAGN ALES— ANDRE JEALES 171 

of very young leaves characteristic glandular hairs are met 
with. They consist of a short basal cell and an enlarged ter- 




minal cell containing a densely granular matter, which from 
its behaviour with stains seems to be mucilaginous. The form 



172 MOSSES AND FERNS chap. 

of the secreting cell is elongated oval (Fig. 89, D), and the 
hair is inserted close to the base of the leaf, upon its inner sur- 
face. 

The young leaf consists of perfectly uniform cells of a 
nearly rhomboidal form (Fig. 90, A), and this continues until 
the apical growth ceases. Then there begins to appear the sep- 
aration into the chlorophyll-bearing and hyaline cells of the 
mature leaf. This can be easily followed in the young leaf, 
where its base is still composed of similar cells, but where 
toward the apex the two sorts of cells become gradually differ- 
entiated. The future hyaline cells grow almost equally in 
length and breadth, although the longitudinal growth some- 
what exceeds the lateral. These alternate regularly with the 
green cells, which grow almost exclusively in length, and form 
a network with rhomboidal meshes, whose interstices are occu- 
pied by the hyaline cells. The latter at first contain chloro- 
phyll, which soon, however, disappears; and finally, as is well 
known, they lose their contents completely, and in most cases 
round openings are formed in their walls. The protoplasm is 
mainly used up in the formation of the spiral and ring-shaped 
thickenings upon the inner surface of the wall, so characteristic 
of these cells (Fig. 90, D). The chlorophyll cells are some- 
times so crowded and overarched by the hyaline ones that they 
are scarcely perceptible, and of course in such leaves the green 
colour is very faint. Cross-sections of the leaves show a char- 
acteristic beaded appearance, the large swollen hyaline cells 
regularly alternating with the small wedge-shaped sections of 
the green cells (Fig. 90, E). Russow (4) has shown that the 
leaves of the sporogonial branch retain more or less their primi- 
tive character, and the division into the two sorts of cells of the 
normal leaves is much less marked. He connects this with the 
necessity for greater assimilative activity in these leaves for 
the support of the growing sporogonium. From his account 
too it seems that the stem leaves lose their activity very early. 

The degree of development of the thickenings upon the 
walls of the hyaline cells varies in different species, and in dif- 
ferent parts of the leaf. It is, according to Russow, best de- 
veloped in the upper half of the leaf, where these thickenings 
have the form of thin ridges projecting far into the cell cavity. 

The development of the central tissue of the stem varies. 



V. MOSSED (MUSCI): SPIIAGNALES—ANDREALALES i73 

The central portion usually remains but little altered and con- 
stitutes a sort of pith composed of thin-walled colourless par- 
enchyma, which merges into the outer prosenchymatous tissue 
of the central region. The cells of the latter are very thich 
walled, and elongated, and their walls are usually deeply stained 
with a brown or reddish pigment. In their earlier stages, ac- 
cording to Schimper ((i), p. 36), the prosenchyma cells have 
regularly arranged and characteristic pitted markings on their 
walls, but as they grow^ older and the walls thicken, these be- 
come largely obliterated. Cross-sections of these prosenchyma 
cells show very distinct striation of the w^all (Fig. 90, G), 
which become less evident as they approach the thinner-walled 
parenchyma of the central part of the stem. No trace of a cen- 
tral cylinder of conducting tissue, such as is found in most of 
the Mosses, can be found in Sphagnum, and this is correlated 
with the absence of a midrib in the leaves. 

The cortex at first forms a layer but one cell thick, but is 
from the first clearly separated from the axial stem tissue. In 
the smallest branches it remains one-layered (Fig. 89, C), but 
in the larger ones it early divides by tangential walls into two 
layers, which at this stage are very conspicuous (Fig. 89, B). 
Later there may be a further division, so that the cortex of the 
main axes frequently is four-layered. While the cells of the 
young cortex are small, and the tissue compact, later there is 
an enormous increase in the size of the cells, which finally lose 
their protoplasmic contents and resemble closely the hyaline 
cells of the leaves. Like the latter, the cortical cells are per- 
fectly colourless, and usually have similar circular perforations 
in their walls. The resemblance is still more marked in S. 
cymhifolinm, where there are spiral thickened bands, quite like 
those of the hyaline leaf cells. On the smaller branches the 
cortical cells (Schimper (i), p. 39), have been found to be of 
two kinds — the ordinary form and curious retort-shaped cells 
with smooth walls and single terminal pore. 

The Branches 

Leitgeb ( i ) has studied carefully the branching of Sphag- 
num, which corresponds closely to the other Mosses investi- 
gated. The branch arises from the lower of the two cells into 



174 MOSSES AND FERNS chap. 

which the outer of the two primary cells of the segment is 
divided. In this cell, which ordinarily constitutes part of the 
cortex, walls are formed in such a way that an apical cell of the 
ordinary form is produced. These lateral branches themselves 
branch at a very early period, and form tufts of secondary ones. 
Schimper was unable to make out clearly what the nature of 
this branching was, but suggested a possible dichotomy. Leit- 
geb, however, concludes that it is monopodial, and that each 
branch corresponds to a leaf, as do the primary branches. The 
growth of all the lateral branches, both the descending flagellate 
ones and the short upright ones at the top of the stem, is limited, 
and lasts through one vegetative period only. This, however, 
is not true of the branches that are destined to continue the axis 
These are apparently morphologically the same as those whose 
growth is limited, but they continue to grow in the same man- 
ner as the main axis. 

The Sexual Organs 

The sexual organs in Sphagnum are produced on branches 
that do not differ essentially from the sterile ones. The leaves 
of the antheridial branches are usually brightly coloured, — red, 
yellow, or dark green, and are closely and very regularly set 
so that the branch has the form of a small catkin (Fig. 91, A). 
The antheridia stand singly in the axils of the leaves, and Leit- 
geb states that their position corresponds with that of branches, 
with which he regards them as homologous, having observed 
in some cases a bud occupying the place of an antheridium. He 
studied in detail their development, which differs considerably 
from that of the other Mosses. The antheridium arises from 
a single cell whose position corresponds to that of a lateral bud 
on an ordinary branch. This cell grows out into a papilla and 
becomes cut ofiF by a transverse wall. The outer cell continues 
to elongate without any noticeable increase in diameter, and a 
series of segments are cut off from the terminal cell by walls 
parallel to its base, so that the young antheridium consists of 
simply a row of cells, comparable to the very young anther- 
idium of the Marchantiacese. Intercalary transverse divisions 
may also arise, and later some or all of the cells, except the ter- 
minal one, divide by longitudinal walls, usually two intersect- 
ing ones in each cell, so that the antheridium rudiment at this 



V. 



MOSSES (MUSCI): SPHAGNALES—ANDREJEALES 175 



stage is composed of a long stalk composed of several rows of 
cells, usually four, and a terminal cell which later gives rise to 



.-cal 





Fig. 91. — A, Male catkin of Sphagnum cymhifoUum, X50; B, young antheridium of 
S. acutifolium, X350; C, opened antheridium of the same species; D, spermatozoid, 
Xiooo (about); E, female branch with sporogonium of S. acutifolium, slightly 
magnified; cal, calyptra. A, C, E, after Schimper; B, after Leitgeb. 



the body of the antheridium. The first divisions in the body 
of the antheridium only take place after the stalk has become 



176 MOSSES AND FERNS chap. 

many times longer than the terminal cell, and is divided into 
many cells. 

The account of the development of the antheridium given 
by Hofmeister and Schimper is incomplete, and differs in some 
respects from that of Leitgeb. Neither of the former observ- 
ers seems to have clearly recognised the presence of a definite 
apical cell from the first. Schimper ( ( i ) , p. 45 ) , states that 
after the stalk has been formed four rows of segments arise 
from the terminal cell; to judge from the somewhat vague 
statements of Hofmeister ((i), p. 154), it appears that he re- 
garded the terminal growth as taking place by the activity of 
a two-sided apical cell, as in other Mosses. Leitgeb states that, 
while this form of growth does frequently occur, usually the 
divergence of the segments is not exactly half, and the segments 
do not stand in two straight rows, but some of them are inter- 
calated between these, forming an imperfect third row. Each 
segment is first divided by a radial wall into nearly equal parts, 
and these are then divided into an outer and an inner cell, and 
from the latter by repeated divisions the sperm cells are formed. 
The body of the full-grown antheridium is broadly oval, and 
both in its position and shape recalls strongly that of such a 
foliose Liverwort as Porella. 

The development of the spermatozoids has been carefully 
followed by Guignard ((i), p. 69), and corresponds in the 
main with that of the Hepaticae. A peculiar feature is the 
presence of a pear-shaped amylaceous mass, firmly attached to 
the posterior coil. This becomes evident at a very early stage 
in the development and remains unchanged up to the time the 
spermatozoids are liberated (Fig. 91, D). The vesicle in 
which it is enclosed collapses, leaving only the large starch 
granule, which finally becomes detached. The free spermato- 
zoid has about two complete coils, and in form recalls that of 
Chara. The cilia are two and somewhat exceed in length the 
body. 

The ripe antheridium is surrounded by a weft of fine 
branching hairs, which Schimper suggests serve to supply it 
with moisture.^ It opens by a number of irregular lobes (Fig. 
91, C), precisely as in Porella, and, like that, the swelling of 
the cells is often so great that some of them become entirely 

^ These are probably the hyphae of a fungus, 



V. MOSSES (MUSCI): SPHAGNALES—ANDRE^ALES \77 

detached. Schimper states that antheridia may l:>e formed at 
any time, but they are more abundant in the late autumn and 
winter. 

The archegonia are found at the apex of some of the short 




Fig. 92. — Sphagnum acutifolium. Development of the embryo (after Waldner). A-D, 
Median optical section; E, F, cross-sections. A, D, E, F, X360; C, X315; D, 
XiS3. 



branches at the summit of the plant, which externally are indis- 
tinguishable from the sterile branches. The development of 
the archegonia has not been followed completely, but to judge 
from the stages that have been observed and the mature arche- 



12 



178 MOSSES AND FERNS chap. 

gonium, its structure and development correspond closely to 
that of the other Mosses. As in these, and the acrogynous 
Hepaticse, the apical cell of the branch becomes an archegonium, 
and a varying number of secondary archegonia arise from its 
last-formed segments. The mature archegonium has a mass- 
ive basal part and long somewhat twisted neck, consisting of 
six rows of cells. As in the other Mosses, the growth of the 
young archegonium is apical, and probably as there the neck 
canals are formed as basal segments of the apical cell, and the 
ventral canal cell is cut off from the central cell in the usual 
way. The venter merges gradually into the neck above and 
the pedicel below^ and at maturity its wall is two or three cells 
thick. The Qgg (Waldner (2)) is ovoid, and the nucleus 
shows a distinct nucleolus. Whether a receptive spot is present 
is not stated. Mixed with the archegonia are numerous fine 
hairs like those about the antheridium. The leaves immedi- 
ately surrounding the group of archegonia later enlarge much 
and form a perichsetium. By the subsequent elongation of 
the main axis both archegonial and antheridial branches are 
often separated by the growth of the axis between them, al- 
though at first they are always crowded together at the top of 
the main stem. 

The Sporophyte 

Waldner (2) has recently studied carefully the develop- 
ment of the embryo of Sphagnum, which differs essentially from 
all the other Mosses, and has its nearest counterpart in the 
Anthocerotes. In the species S. acutifolium, mainly studied by 
Waldner, the sexual organs are usually mature in the late au- 
tumn and winter, and fertilisation occurs early in the spring. 
The ripe sexual organs are found in a perfectly normal condi- 
tion in mid-winter, under the snow, and apparently remain in 
this condition until the first warm days, when they open and 
fertilisation is effected. The first embryos were found late in 
February, and development proceeded from that time. 

The first division in the embryo is horizontal and divides it 
into two cells. In the lower of these the divisions are irregu- 
lar, but in the upper one the cell walls are arranged with much 
regularity. The upper cell is the apical cell of the young em- 
bryo, and from it, by walls parallel to the base, a series of seg- 



V. MOSSES (MUSCI): SPHAGNALES—ANDRE/EALES i79 

ments is formed (Fig. 92, A). These are usually about seven 
in number, and each of these segments undergoes regular divi- 
sions, these beginning in the lower ones and proceeding toward 
the apical cell, which finally ceases to form basal segments and 
itself divides in much the same way as the segments. The 
latter first divide by two vertical divisions into quadrants, and 
in each quadrant either directly l)y periclinal walls, or by an 
anticlinal wall followed by a periclinal wall in the inner of the 
two cells (Fig. 92, E), four central cells in each segment are 
separated from four or eight peripheral ones. The terms cn- 
dotheciuni and amphithccium have been given respectively to 
these two primary parts of the young Moss-sporogonium. By 
the time that the separation of endothecium and amphithecium 
is completed, a division of the embryo into two regions becomes 
manifest (Fig. 92, C). Only the three upper segments, in- 
cluding the apical one, give rise to spores ; the lower segments 
together with the original basal cell of the embryo form the 
foot, which in Sphagmim is very large. The cells of the foot 
enlarge rapidly and form a bulbous body very similar in appear- 
ance and function to that of Notothylas or Anthoccros. The 
next divisions too in the upper part of the sporogonium find 
their nearest analogies in these forms. The central mass of 
cells, both in position and origin, corresponds to the columella 
in these genera, and the archesporium arises by the division of 
the amphithecium into two layers by tangential walls, and the 
inner of these tw^o layers, in contact with the columella, becomes 
at once the archesporium. By rapid cell division the upper 
part of the sporgonium becomes globular, and is joined to the 
foot by a narrow neck, much as in Notothylas (Fig. 93). The 
single-layered wall of the young sporogonium becomes six or 
seven cells thick, and the columella very massive. The one- 
layered archesporium also divides twice by tangential walls, 
and thus is four-layered at the time the spore mother cells sep- 
arate. i\ll the cells of the archesporium produce spores of the 
ordinary tetrahedral form. The so-called ''microspores" have 
been shown conclusively to be the spores of a parasitic fungus 
(Nawaschin (i)). The layer of cells in immediate contact 
with the archesporium on both inner and outer sides has more 
chlorophyll than the neighbouring cells, and forms the 
"spore-sac." 



i8o 



MOSSES AND FERNS 



CHAP. 



The ripe capsule opens by a circular lid which is indicated 
long before it is mature. The epidermal cells where the open- 
ing is to occur grow less actively than their neighbours, and 
thus a groove is formed which is the first indication of the oper- 
culum. The cells at the bottom of the groove have thinner 

walls than the other cells 
of the capsule wall, and 
when it ripens these dry 
up and are very readily 
broken, so that the oper- 
culum is very easily sep- 
arated from the dry cap- 
sule. Stomata, according 
to Schimper, always are 
present, sometimes in 
great numbers; but Hab- 
erlandt ((4), p. 475 )> 
states that these are al- 
ways rudimentary, and 
he regards them as re- 
duced forms. No seta is 
formed, but its place is 
taken physiologically by 
the upper part of the axis 
of the archegonial branch, 
which grows Up beyond 
the perichaetium, carrying 
the ripe sporogonium at 
its top (Fig. 91, E). The 
upper part of this ''pseu- 
dopodium" is much en- 
larged, and a section through it shows the bulbous foot of the 
capsule occupying nearly the whole space inside it. The ripe 
capsule breaks through the overlying calyptra, the upper part 
of which is carried up somewhat as in the higher Mosses, while 
the basal part together with the upper part of the pseudopodium 
forms the 'Vaginula." 

The disorganised contents of the canal cells, which are 
usually ejected from the archegonium, in Sphagnum remain in 
a large measure in the central cavity, and on removing the 




Fig. 93. — Median longitudinal section of a 
nearly ripe sporogonium of S. acutifoli- 
urn, X24; ps, pseudopodium; sp, spores; 
col, columella (after Waldner). 



V. MOSSES (MUSCI): SPHAGNALES—ANDREJEALES i8i 

young embryo from the venter of the archegonium, this muci- 
laginous mass adheres to it and forms a more or less complete 
envelope about it, in which are often found the remains of 
spermatozoids. 

The species of Sphagmim are either monoecious or dirjecious, 
but in no cases do archegonia and antheridia ocair upon the 
same branch. 

The Andre^ales 

The second order of the Mosses includes only the small 
genus Andrecoa, rock-inhabiting Mosses of small size and dark 




A. 




Fig. 94. — AndrecPa petrophila. A, Plant with ripe sporogonium, Xio; B, median sec- 
tion of nearly ripe capsule, X8o; ps, pseudopodium; coi, columella. 



brown or blackish colour. In structure they are intermediate 
in several respects between the Sphagnales and the Bryales, 
as has been shown by the researches of Kiihn (i), and W'ald- 
ner (2), to whom we owe our knowledge of the life-history of 
Andrecea. They all grow in dense tufts upon silicious rocks, 



i82 MOSSES AND FERNS chap. 

and are at once distinguished from other Mosses by the dehis- 
cence of their small capsules. These, like those of Sphagnum, 
are raised upon a pseudopodium, and are destitute of a true 
seta. The capsule opens by four vertical slits, which do not, 
however, extend entirely to the summit (Fig. 94). This 
peculiar form of dehiscence recalls the Jungermanniacese, but is 
probably only an accidental resemblance. The closely-set stems 
branch freely; the leaves, with three-eighth divergence, are 
either with a midrib (A. riipestris) or without one {A, 
petrophila). 

The growth of the stem is from a pyramidal apical cell, as 
in Sphagnum, and probably the origin of the branches is also 
the same as in that genus. The growth of the young leaves is 
usually from a two-sided apical cell, but another type of growth 
is found where the apical cell is nearly semicircular in outline, 
and segments are cut off from the base only. These two forms 
of apical growth apparently alternate in some instances in the 
same leaf. The originally thin walls of the leaf cells later be- 
come thick and dark-coloured, whence the characteristic dark 
colour of the plant. 

The stem in cross-section shows an almost uniform struc- 
ture, and no trace of'the central conducting tissue of the higher 
Mosses can be found. The outer cells are somewhat thicker- 
walled and darker-coloured, but otherwise not different from 
the central ones. Numerous rhizoids of a peculiar structure 
grow from the basal part of the stem, and from these, new 
branches arise, which replace the older ones as they die away. 
These rhizoids are not simple rows of cells as in the Bryales, 
but are either cylindrical masses of cells or flattened plates. 
They penetrate into the crevices of the rocks, or apply them- 
selves very closely to the surface, so that the plants adhere 
tenaciously to the substratum (Ruhland (2)). 

Spores and Protonema 

The germination of the spores and the development of the 
protonema show numerous peculiarities. The spores may 
germinate within a week, or sometimes remain unchanged for 
months. They have a thick dark-brown exospore and contain, 
chlorophyll and oil. The first rdivisions take place before the- 
exospore is ruptured, and may §€ in thrfie planes, so that the 



V. 



MOSSES (MUSCI): SPHAGNALES—ANDRE^ALES 183 



young protonema then has the form of a globular cell mass 
(Fig. 95, A). This stage recalls the corresponding one in 
many of the thallose Hepaticae, e. g., Pellia, Rachila, and is 
entirely different from the direct formation of the filamentous 
protonema of most Mosses. Some of the superficial cells of 
this primary tubercle grow out into slender filaments, either 
with straight or oblique septa, and these later ramify exten- 
sively. Where there are crevices in the rock, some of these 
branches grow into them as colourless rhizoids. but, as in the 
Bryales, there is no real morphological distinction between 
rhizoid and protonema. Most of the filamentous protonema! 
branches do not remain in this condition, but become trans- 
formed into cell plates or cylindrical cell masses, like the stem- 





FiG. 95. — A, B, Germinating spores of A. petrophila, X200; C, protonema with bud 
(fe); D, young archegonium in optical section; E, i, 2, two views of a very young 
embryo of A. crassinerva, X266; F, somewhat older embryo of A. petrophila; G, 
older embryo showing the first archesporial cells; H, I, cross-sections of young 
embryos, X200. A-D, after Kuhn; E-I, after Waldner. 



rhizoids. The flat protonema recalls strongly that of Sphag- 
num, and is probably genetically connected with it. All of the 
different protonemal forms, except what Kiihn calls the ''leaf- 
like structures," vertical cell surfaces of definite form, can give 
rise to the leafy axes. The development of these seems to cor- 
respond exactly with that of the other Mosses, and will not be 
further considered here. 



i84 MOSSES AND FERNS chap. 

The Sexual Organs 

The species of Andrecea may be either moncecious or dioe- 
cious. Archegonia and antheridia occur on separate branches, 
but their origin and arrangement are identical. The first- 
formed antheridium develops directly from the apical cell of the 
shoot, and the next older ones from its last-formed segments, 
but beyond this no regularity can be made out. In the first one 
the apical cell projects, and its outer part is separated from the 
pointed inner part by a transverse wall. This is followed by a 
second wall parallel to the first, so that the antheridium rudi- 
ment is composed of three cells. Of these the lower one takes 
little part in the future development. Of the two upper cells 
the terminal one becomes the body of the antheridium, the other 
the stalk. In the former, by two inclined walls, a two-sided 
apical cell is developed, and the subsequent growth is the same 
as in the Bryales. The middle cell of the antheridium rudi- 
ment divides repeatedly by alternating transverse and longi- 
tudinal walls, and forms the long two-rowed stalk of the mature 
antheridium. On comparing the antheridium with that of the 
other Mosses, we find that it approaches Sphagnum in the long 
stalk, but in its origin and the growth of the antheridium itself, 
it resembles closely the higher Mosses. 

The first archegonium also is derived immediately from the 
apical cell of the female branch, and the first divisions are the 
same as in the first antheridium. Here, too, the subsequent 
development corresponds exactly with that of the higher 
Mosses, and will be passed over. The ripe archegonium shows 
no noteworthy peculiarities, and closely resembles in all respects 
that of the other Mosses. 

The Sporophyte 

The more recent researches of Waldner (2) on the develop- 
ment of the sporogonium of Andrecea have shown clearly that 
in this respect also the latter stands between the Sphagnacese 
and the Bryales. The first division in the fertilised ovum is 
transverse and divides it into two nearly equal parts. The 
lower of these divides irregularly and much more slowly than 
the upper one. In the latter (Fig. 95, E), the first division 
wall is inclined, and is followed by a second one which meets 
it nearly at right angles, and by walls inclined alternately right 



V. MOSSES (MUSCI): SPHAGN ALES— ANDRE JEALES 185 

• 

and left — in short, has the character of the famiHar *'two-sIded" 
apical cell. The number of segments thus formed ranges from 
eleven to thirteen. Each segment is first divided by a vertical 
median wall into equal parts, so that a cross-section of the 
young embryo at this stage shows four equal quadrant cells. 
The next divisions correspond to those in Sphagnum, and result 
in the separation of the endothecium and amphithecium. The 
formation of the archesporium, however, differs from Sphag- 
num, and is entirely similar to that of the higher Mosses. In- 
stead of arising from the amphithecium as in the former, the 
archesporium is formed by the separation of a single layer of 
cells from the outside of the endothecium. All of the segments 
do not form spores, but only three or four, beginning wnth the 
third from the base. The two primary segments of the upper 
part of the embryo, like the corresponding ones in Sphagnum, 
go to form the foot, which is not so well developed, however, 
as in the latter. The originally one-layered archesporium later 
becomes double, and as in Sphagnum extends completely over 
the columella, which is thus not continuous with the tissue of 
the upper part of the sporogonium. As in Sphagnum also, no 
trace of the intercellular space formed in the amphithecium of 
the Bryales can be detected. A section of the nearly ripe cap- 
sule shows the club-shaped columella extending nearly to the 
top of the cavity. With the growth of the capsule the space 
between the inner and outer spore-sacs becomes very large to 
accommodate the growth of the numerous spores. The pseu- 
dopodium is exactly the same as in Sphagnum, and the vaginula 
and calyptra are present. The latter is much firmer than in 
Sphagnum, and like that of the Bryales. 

Archidium 

The genus Archidium is one whose systematic position has 
been long a subject of controversy. It has usually been associ- 
ated with the so-called cleistocarpous Bryales, but the researches 
of Leitgeb (8) seem to point to a nearer affinity wuth Andrecca, 

The species of Archidium are small Mosses growing on the 
earth, and especially characterised by the small number, but 
very large size, of the spores contained in the sessile globular 
sporogonium. Hofmeister ( ( i ) , p. 160), was the first to study 
the development, and his account agrees in the main with Leit- 



i86 



MOSSES AND FERNS 



CHAP. 



geb's, except as to the relation of the columella and outer spore- 
sac. The first divisions in the embryo correspond exactly to 
those in Andrecua and the Bryales, and for a time the young 
embryo grows from a two-sided apical cell. The secondary 
divisions in the segments, however, are quite different from that 
observed in any other Moss, and are like those in the anther- 
idium. Instead of the first wall dividing the segment into 
equal parts, it divides it very unequally. The second wall 
strikes this so as to enclose a central cell, triangular in cross- 




FiG. 96. — Archidium Ravenelii. A, Median section through a nearly ripe sporogonium, 

X90; B, base of the sporogonium, X27o. 



section, which with the corresponding cell of the adjacent seg- 
ment forms a square. This square, the endothecium, does not 
therefore at first show the characteristic four-celled stage found 
in all other Mosses. The amphithecium becomes ultimately 
three-layered, and between the second and third layers an inter- 
cellular space is formed, as in the Bryales, but this extends com- 
pletely over the top of the columella. The most remarkable 
feature, however, is that no archesporium is differentiated, but 
any cell of the endothecium may apparently become a spore 



V. MOSSES (MUSCI): SPIIAGMALES—ANDRnjEALES 187 

mother cell. The number of the latter is very small, seldom 
exceeding five or six. They become rounded off, and gradu- 
ally displace the other endothecial cells, which doubtless serve 
as a sort of tapetum for the nourishment of the growing spores. 
Each spore mother cell as usual gives rise to four spores, which 
are very much larger than in any other Moss. A section of 
the ripe sporogonium (Fig. 96), shows that only one of the 
primary three layers of amphithecial cells can be recognised 
except at the extreme apex and base. No seta is present, and 
a foot much like that of Andrecea, and penetrating into the tis- 
sue of the stem apex, is seen. 

Leitgeb is inclined to look upon Archidinm as a primitive 
form allied on the one hand to Andrecca and on the other to 
the Hepatic^, possibly Notothylas. However, as his assump- 
tion that the latter has no primary columella has been shown to 
be erroneous, his comparison of the w-hole endothecium of Ar- 
chidiuni wath that of Notothylas cannot be maintained, as we 
have shown that in the latter, as in Anthoceros, the arche- 
sporium arises from the amphithecium, and not from the en- 
dothecium, as is the case in Archidinm. Inasmuch as the game- 
tophyte and sexual organs of Archidinm are those of the typical 
Mosses, it seems quite as likely that the older view that Ar- 
chidium is a degenerate form is correct. At any rate, until 
more convincing evidence can be brought forward in support 
of a direct connection between it and the Hepaticae than the 
formation of the spores directly from the central tissue of the 
sporogonium, it cannot be said that the question of its real affin- 
ities is settled. 



CHAPTER VI 

THE BRYALES 

Under the name Bryales may be included all the other Mosses ; 
for. although the so-called cleistocarpous forms are sometimes 
separated from the stegocarpous Mosses as a special order, the 
Phascacese, the exact correspondence in the development of 
both the gametophyte and sporophyte shows that the two groups 
are most closely allied, the former being either rudimentary or 
degraded forms of the others. 

With few exceptions the protonema is filamentous and 
shows branches of two kinds, the ordinary green ones with 
straight transverse septa, and the brown-walled rhizoids with 
strongly oblique ones, but the two forms merge insensibly into 
one another, and are mutually convertible. In a few forms, 
notably the genus Tetraphis, the protonema is thalloid, and as 
in Sphagnum these flat thalli give rise to filamentous proto- 
nemal threads, which in turn may produce secondary thalloid 
protonemata. The genus Diphyschim (C. Muller (3), pp. 
169, 170), develops upon the protonema solid, trumpet-shaped 
bodies. In some of the simpler forms, e. g., Ephemerum, the 
protonema is permanent, and the leafy buds appear as append- 
ages of it ; but in most of the larger Mosses the primary proto- 
nema only lives long enough to produce the first leafy axes, 
which later give rise to others by branching, or else by second- 
ary protonemal filaments growing from the basal rhizoids. 
The early stages of development of the primary protonema are 
easily traced, as the spores of most Mosses germinate readily 
when placed upon a moist substratum. The ripe spores usually 
contain abundant chlorophyll and oil, and the thin exospore is 
brown in colour. The spore absorbs water and begins to en- 
large until the exospore is burst, when the endospore protrudes 

188 



CH. VI. 



THE BRYALES 



189 



as a papilla which grows out into a filament ; or the endospore 
sometimes grows out in two directions, and one of the papillcC 
remains nearly destitute of chlorophyll and forms the first rhi- 
zoid. The growth of the protonemal filaments is strictly 
apical, no intercalary divisions taking place except those by 
which lateral branches arise. If abundant moisture is present, 
the protonema grows with great rapidity and may form a dense 
branching alga-like growth of considerable extent. Sooner or 
later upon this arise the leafy gametophores. The develop- 
ment of the latter, as we have seen, also takes place abundantly 




gam.. — 



Fig. 97. — Funaria hygrometrica. A, Fragment of a protonemal branch with a young 
gametophoric bud; r, rhizoid; B, median optical section of the bud; C, older bud — • 
I, surface view; 2, optical section; x, apical cell; D, protonema with a still older 
gametophore (^gam) attached. A-C, X225; D, X36. 



from the secondary protonemal filaments which may be made to 
grow from almost any part of the gametophore. 

The development of the bud is as follows. From a cell of 
the protonema a protuberance grows out near the upper end. 
This is at first not distinguishable from a young protonemal 
branch, but it very soon becomes somewhat pear-shaped, and 
instead of elongating and dividing simply by transverse walls, 
the division walls intersect so as to transform it into a cell mass. 



190 MOSSES AND FERNS chap. 

After the cell is separated it is usually divided at once by a 
strongly oblique wall, which is then intersected by two others 
successively formed and meeting each other and the first- formed 
one at nearly equal angles, so that the terminal cell of the young 
bud (Fig. 97, A), has the form of an inverted pyramid; that 
is, by the first divisions in the bud the characteristic tetrahedral 
apical cell of the gametophore is established. From now on 
the apical cell divides with perfect regularity, cutting off three 
sets of lateral segments. From the base of the young gameto- 
phore the first rhizoid (Fig. 97, A, r ), is formed at a very early 
period. The first two or three segments do not give rise to 
leaves, and the leaves formed from the next younger segments 
remain imperfect. Thus in Funaria hygrometrica these earliest 
formed leaves show no midrib. The young leaves rapidly 
elongate and completely cover up the growing point of the 
young bud, and are at first closely imbricated. Later, by the 
elongation of the axis, the leaves become more or less completely 
separated (Fig. 97, C, D). In Funaria, as well as in many 
other Mosses, buds are often met with that have become arrested 
in their development, lost their chlorophyll, and assumed a dark- 
brown colour. This arrest often seems to be the result of un- 
favourable conditions of growth, and under proper conditions 
these buds probably always will develop either directly or by 
the formation of a secondary protonema into perfect plants. 

Apical Growth of the Stem 

The growth of the stem of the fully-developed gametophore 
is better studied in one of the larger Mosses. The growth of 
the gametophore is so limited in length in Funaria that it is 
not so well adapted for this. Perhaps the best species for this 
purpose is the well-known Fontinalis antipyretica, which has 
already been carefully studied by Leitgeb ( i ) . Amhlystegium 
riparium, var. Uuitans, was examined by me and differed in 
some points from Leitgeb' s figures of Fontinalis. Fig. 98, A 
shows an exactly median longitudinal section through a strong 
growing point. Compared with Leitgeb's figures the apical cell 
is much deeper than in Fontinalis, and in consequence the young- 
segments more nearly vertical. Here, as in Sphagnum, the first 
wall in the young segment divides it into an inner and an outer 
cell, from the latter of which alone are formed the lateral 



VI. 



THE BRYALES 



191 



appendages of the stem. The inner cells of the segments by 
repeated longitudinal and transverse divisions form all the tis- 
sues of the axis. The second division wall in the segment, like 
that in Sphagnum, is at right angles to the first, but in Ambly- 
stcgmm it extends the whole breadth of the segment. By this 
division the outer of the two primary cells of the segment is 
divided into an upper cell, from which the leaf develops, and a 
lower one from which the outer part of the stem and the burls 
are formed. The leaves grow from a two-sided apical cell 




Fig. 98. — Amblystegium riparium, var. fluitans. A, IMedian longitudinal section of a 
strong shoot; x, apical cell; x', initial of a lateral branch, X250; B, transverse 
section through the apex, X250; C, similar section through a young branch, Xsoo* 



(Fig. 99), as indeed they seem to do in all Mosses, and the 
divisions proceed w^ith great rapidity and the young leaves 
quickly grow beyond and surround the growing point. In 
Amblystegiiun, as in all the typical Bryalcs, the leaf has a well- 
developed midrib. The formation of this begins while the leaf 
is very young and proceeds from the base. In the middle row 
of cells (Fig. 99, C), a w^all first arises parallel to the surface 
of the leaf, and this is follow^ed by a wall in the cell on the lower 
side of the leaf (Fig. 99, D). By further divisions in all the 



192 



MOSSES AND FERNS 



CHAP. 



cells of this central strand the broad midrib found in the mature 
leaf is developed. In Amhlystegiwn all the cells of the midrib 
are, alike and have thickened walls. The midrib projects on both 
sides of the leaf, but rather more strongly upon the lower side. 
In Funaria (Fig. loo), the structure of the midrib Is more 
definite. Here two rows of cells take part in the formation of 
the midrib. Each of these first divides as in Amblystegium by 
a wall parallel to the surface of the leaf, so that in cross-section 
the central part of the leaf shows a group of four cells, those 





Fig. gg.— 'Amblystegium riparium, var. fiuitans. A, Longitudinal section of the stem 
passing through a young lateral branch {k) ; h, hair at the base of the subtending 
leaf; B, horizontal sec+^^ion of a very young leaf, showing the apical cell (,x) ; C, 
D, transverse sections of young leaves, showing the development of the midrib. 
All the figures X525. 



on the outer side being larger than the others. In the former 
the next wall is a periclinal one and divides the cell into an inner 
and an outer one. From the two inner cells by further division 
is formed the group of small conducting cells that traverse the 
centre of the midrib, while the outside cells together with those 
on the inner side of the midrib become much thickened and 
serve for strengthening the leaf. As in Amblystegium the 
lamina of the leaf remains single-layered, and its cells contain 
numerous large chloroplasts which, as is well-known, continue 



VI. 



THE BR VALES 



193 



to multiply by division after the cells are fully f^rown. The 
marginal cells in the leaf of Funoria are much narrower than 
those between them and the midrib, and their forward ends 




Fig. 100. — Funaria hysrometrica. A, Transverse section of the apex of a young shoot, 
X515; B, C, cross-sections of young leaves, X515; D, cross-section of the stem, 
X257. 

often project somewhat, giving the margin of the leaf a serrate 
outline, which is also common in many other Mosses. 



The Branches 

For the study of the branching of the stem, Amhlystcgunn 
again is much better than Funaria, wdiose short stem and infre- 
quent branching makes it difficult to find the different stages. 
In Amblystegiuiu, however, every median section will show 
some of the stages, and it is easy to follow out all the details, 
as has already been done in Fontinalis by Leitgeb. The lateral 
shoot originates from a basal cell of the segment below the 
middle of the leaf. It is very easily seen that it belongs to the 
13 



194 MOSSES AND FERNS chap. 

same segment as the leaf standing above it, and therefore is 
not axillary in its origin. The mother cell of the young branch 
projects above the surrounding cells, and in it are formed in 
succession three oblique intersecting walls which enclose the 
narrow pyramidal apical cell (Figs. 98, 99). The secondary 
divisions in the first set of segments are not so regular as in 
the later ones, but the bud rapidly grows, and very soon the 
perfectly regular divisions of the young segments are estab- 
lished. So far as investigations have been made upon other 
genera, they follow the same line of development as Ambly- 
stegium, Fontinalis, and Sphagnum. 

Where the growth of the main axis is stopped by the form- 
ation of sexual organs, a lateral branch frequently grows out 
beyond the apex of the main axis, as in Sphagnum, and thus 
sympodia arise. In other cases, where the growth of the lat- 
eral branches is limited, characteristic branch systems arise, 
such as we find in Thuidium or Climacium (Fig. 86). 

Compared with Amhlystegium, the growing point of 
Funaria and other Mosses of similar habit is much broader, 
and the apical cell not so deep. The arrangement of the 
segments is much the same, except that the original three- 
ranked arrangement of the segments which is retained in Fonti- 
nalis^ is replaced in most Mosses by a larger divergence, owing 
to a displacement like that in Sphagnum. 

A cross-section of the older stem (Fig. 100, D), shows in 
most Bryales a central cylinder of small thin-walled cells sur- 
rounded by a large-celled cortical tissue, which in the older 
parts of the stem often has its walls strongly thickened and 
reddish brown in colour. An epidermis, clearly recognisable 
as such, cannot usually be detected. The outer cells contain 
chlorophyll, which is wanting in the central cylinder. 

The rhizoids in Funaria grow mainly from the base of the 
stem, and the first ones arise very soon after the young bud is 
formed. Their growth, like that of the protonemal branches, 
is strictly apical, and they branch extensively. The young ones 
are colourless, but as they grow older the walls assume a deep 
brown colour. Usually the division walls in the rhizoids are 
strongly oblique. Their contents include more or less oil, and 
where they are exposed to the light, chlorophyll. 

^ This is only strictly true in the smaller branches. 



VI. 



THE BRYALES 

The Sexual Organs 



195 



Funaria is strictly dioecious. The male plants (Fig. loi, 
A) are easily distinguished by their form. They are about I 
cm. in height, with the lower leaves scattered, but the upper 




«3 





r T rt 

■' P" 
c .a 



c .s 

c .t; 

^> 

u 

« .2 

C bo 

s o 

>> 9, 









•- <j 

X -^ 

. X 

c « 

J2 H 
c 3 

O C 

S o • 
<< u n 

.0,1-1 

'^ >, ° 
"St" 

^ .^ >^^# 

.2 '^ 

*> •" _r 

O C t3 

K C3 « 



a o 
B 



»4 cd 

o 



ones crowded so as to present much the appearance of a flower 
whose centre forms a small reddish disc. These male plants 
either grow separately or more or less mixed with the females. 



196 



MOSSES AND FERNS 



ciiw. 



Whether the first antheridium, as in Andrecea and Fontinalis, 
arises from the apical cell is doubtful, and it is impossible to 
trace any regularity in the order of formation of the very 
numerous antheridia. Except in old plants, all stages of de- 
velopment are found together, and the history of the anther- 
idium may be easily followed. A superficial cell projects above 
its neighbours, and this papilla is cut off by a transverse wall. 





Fig. 102. — Funaria hygrometrica. Development of the antheridium. A-D, Longitudinal 
sections of young stages, X600; D is cut in a plane at right angles to C; E, optical 
section of an older stage, X300; G, F, cross-sections of young antheridia, X600; 
H, diagram showing the first divisions in the antheridium; I, young spermatozoids, 
X1200. 



The outer cell either becomes at once the mother cell of the 
antheridium, or other transverse walls may occur, so that a 
short pedicel is first formed (Fig. 102, A). Finally in the 
terminal cell, as in Andrecea, two intersecting walls are formed' 
enclosing a two-sided apical cell, from which two ranks of seg- 
ments are cut off in regular succession (Figs. A, B, C). The 
number of these segments is limited, in Funaria not often ex- 
ceeding seven, and after the full number has been formed, the 



VI. THE BRYALES 197 

apical cell is divided by a septum parallel with its outer face 
into an inner cell, which with the inner cells ni the se<(nients 
forms the mass of sperm cells, and an outer cell which prc^luces 
the upper part of the wall. Before the full number is com- 
pleted, the secondary divisions begin, ])roceeding from the base 
upward. These are very regular, and correspond closely to 
those in the antheridium of the Jungermanniaceae, and can only 
be clearly made out by comparing transverse and vertical sec- 
tions of the young antheridium. Fig. 102, H, shows a diagram 
illustrating this : i is the wall separating two adjacent seg- 
ments, and 2 the first wall formed in the segment itself. The 
wall 2, it will be seen, starts near the middle of the periphery 
of the segment and strikes the wall i far to one side of the 
centre, so that the segment is thus divided into two cells of very 
unequal size, although their peripheral extent is nearly equal. 
The next wall (3) strikes both the w^all i and 2 at about equal 
distances from the periphery, and thus each segment is divided 
into an inner cell wdiich in cross-section has the form of a tri- 
angle, and two peripheral cells. The latter divide only by 
radial walls, and give rise to the single-layered wall of the 
antheridium. The inner cells of the segments by further di- 
vision in all directions form the mass of sperm cells. The first 
division w^all in the central cell starts from near the middle of 
the segment wall and curves slightly, so that the two resulting 
cells are unequal in size. From this first division wall usually 
two others having a similar form extend to the peripheral cells, 
and these are next followed by others nearly at right angles 
to them. After this transverse and longitudinal walls succeed 
with such regularity that the limits of the primary segments 
remain perfectly evident until the antheridium is nearly full 
grown. 

The central cells in the fresh antheridium are strongly re- 
fringent and in stained sections show^ a much more granular 
consistence than the outer ones. The nucleus, as in other cases 
studied, loses its nucleolus before the formation of the sperma- 
tozoids begins. The latter in their structure and development 
correspond with those of Sphagnum, but owing to their smaller 
size are not favourable for studying the minute details of de- 
velopment. 

In the peripheral cells are numerous chloroplasts which in 
the ripe antheridiu.m lie close to the inner w^all of the cell As 



198 



MOSSES AND FERNS 



CHAP. 



the antheridium ripens, these gradually assume a bright orange- 
red colour. The development of the stalk varies in different 
cases. Sometimes it consists of a row of several cells, some- 
times the antheridium is almost sessile. The lowermost seg- 








B. 





li 



Fig. 103. — Funaria hygrometrica. A, Antheridium that has just discharged the mass 
of sperm cells (B), X300; C, spermatozoids, X1300; D, paraphysis, X300; E, 
male "flower" of Atrichum undulatum, X6. 



ments of the apical cell help to form the upper part of the 
stalk, and sometimes the two lowest seem to take no part in the 
formation of the sperm cells. There is no absolute uniformity 
in the cell divisions of the stalk, which varies in the arrange-;; 



VI. THE BRYALES igg 

ment of the cells in different individuals in the same inflor- 
escence. 

The ripe antheridium opens promptly when placed in water. 
At the apex there is usually ])resent a single cell decidedly 
larger than its neighbours (Fig. 103, A), or sometimes there 
are two opercular cells (Goebel (22), p. 239). All of the 
parietal cells become strongly turgescent and this is especially 
the case in the terminal cell, which finally bursts and forms a 
narrow opening through which the mass of sperm-cells is forced 
out by the pressure of the distended parietal cells, and the swell- 
ing of the mucilage derived from the disintegration of the walls 
of the sperm-cells. The opercular cell in Punaria is not de- 
stroyed, as a rule, and is still very conspicuous after the sperm- 
cells have been discharged, so that the empty antheridium, ex- 
cept for a slight contraction of its lower part, looks very much 
as it did before the escape of the sperm-cells. In some other 
Mosses, e. g., Polytrichum, Catharinia, the opercular cap con- 
sists of several cells (Goebel, 1. c). The whole mass of sperm- 
cells is thrown out without separating the cells, and in this 
stage the walls of the sperm-cells are still very evident. It 
sometimes happens that the mass is thrown out before the 
spermatozoids are complete, in w^hich case they never escape. 
If, however, the spermatozoids are mature, they show active 
motion within the sperm-cells while these are still in connection, 
and are set free by the gradual dissolution of the mucilaginous 
walls. The free spermatozoid is much like that of Sphagnum, 
but the body is somewhat shorter. The cilia are relatively 
very long and thick, and as in all Bryophytes but two in num- 
ber. A small vesicle can usually be seen attached to the pos- 
terior end. 

Growing among the antheridia are found peculiar sterile 
hairs, or paraphyses. These in Funaria are very conspicuous, 
and, consist of a row of cells tapering to the base, and very 
much larger at the apex. The terminal cell, or sometimes two 
or three of them, are almost globular in form and very much 
distended. All the cells of the paraphyses contain large 
chloroplasts, which in the globular end cells are especially con- 
spicuous and are often elongated with pointed ends. 

The archegonia are formed while the female plant is still 
very small, and it Is much more difficult to recognise the female 
plants than the males. The archegonia are ripe at a time when 



20Q 



MOSSES AND FERNS 



CHAP. 



the female plant is still but a few millimetres in height. In this 
case there is no doubt that the apical cell forms an archegoniuni 
directly, but not necessarily the first one, which arises usually 
from one of the last- formed segments. The elongation of the 
axis of the female branch is but slight, even in the later stages, 




Fig. 104.— Longitudinal section through the apex of a male plant of F. hygrometrica, 

X300; L, leaf; (^, antheridia; p, paraphyses. 

and the plant remains bud-like even after the sporogonium is) 
developed. In regard to the development of the leafy axis, ob 
gametophore, therefore, Funaria offers a very marked contrast?, 
to Fontinalis or Sphagnum, where the gametophore reaches 
such a large size and has practically unlimited growth. 

The young archegonia are quite colourless, and the details; 



VI. 



THE BRYALES 



201 



of their structure may ])e made out without difficulty. The 
first division separates a basal cell from a terminal cell, which 
is the mother cell of the archegonium. In the latter three walls 




now arise, as in tlic Hepaticse and Andrecra, but in Fiinaria 
these do not all reach to the basal wall, but intersect at some 
distance above it, so that they enclose a tetrahedral cell, pointed 



202 MOSSES AND FERNS chap. 

below instead of truncate. The tetrahedral cell now divides 
by a transverse wall into an upper cell, corresponding to the 
''cover cell" of the Liverwort archegonium, and an inner one 
(Fig. 105, A), which gives rise to the primary neck canal cell, 
the egg, and the ventral canal cell. From this point, however, 
the development proceeds in another way, and follows the 
course observed in Andrecea. The cover cell, instead of divid- 
ing by quadrant walls, has a regular series of segments cut off 
from it, and acts as an apical cell. These segments are cut off 
parallel both to its lateral faces and base, and thus form four 
rows of segments, the three derived from the lateral faces 
forming the outer neck cells, and the row of segments cut oft' 
from the base constituting the axial row of neck canal cells. 
Each row of lateral segments is divided by vertical walls, and 
forms six row^s, w^hich later divide by transverse walls as well 
so that the number of cells in each row exceeds the original 
number of segments. This is not the case with the canal cells, 
which, so far as could be determined, do not divide after they 
are first formed. The wall of the venter owes its origin en- 
tirely to the three peripheral cells formed by the other primary 
walls in the archegonium mother cell. This becomes two-lay- 
ered before the archegonium is mature, and is merged gradu- 
ally into the massive pedicel, which in the Mosses generally is 
much more developed than in the Hepaticse. In the older 
archegonia the neck ceJls, do not stand in vertical rows, but are 
somewhat obliquely placed, owing to a torsion of the neck dur- 
ing its elongation. From the central cell the ventral cia'nal cell 
is cut off, as usual, but is relatively smaller than is usual among 
the Hepaticse. The egg shows a distinct receptive spot, which 
is not, however, very large. The rest of the egg shows a 
densely granular appearance, and the moderately large nucleus 
shows very little colourable contents, beyond the large central 
nucleolus. The terminal cells of the open archegonium diverge 
widely, giving the neck of the archegonium a trumpet shape 
(Fig. 105, F). Usually some of the cells become detached and 
are thrown off. 

Holferty ( i ) has made a careful study of the archegonium 
in Mnium cuspidaHim and finds that the archegonium in its 
earliest stages grows from a two-sided initial cell like that of 
the antheridium. This is later replaced by the usual tetra- 
hedral apical cell found in other species. After a more or less 



VI. THE BRYALES 203 

massive pedicel is formed, the apical cell divides, as in fnnaria, 
into an inner and an outer cell. The former, as usual, ^ives 
rise to the central cell, from which later arise the egg" and ven- 
tral canal cell, and a second cell, which is the primary neck 
canal cell. The latter, according to Ilolferty, undergoes fur- 
ther divisions and the secondary canal cells, cut off from the 
base of the apical cell, also undergo further divisions. There 
may be as many as ten neck canal cells finally developed. 

Holferty also describes and figures several abnormal struc- 
tures, intermediate in character between the archegonium and 
antheridium. 

While in Fnnaria and Polytrichnm the plants are regularly 
dioecious, in many Mosses this is not the case. Both antheridia 
and archegonia may occur in the same "inflorescence," or they 
may be in separate groups upon different parts of the same 
plant. Some doubt has been thrown upon the nature of the so- 
called hermaphrodite inflorescences, and it is possible that they 
are really composed of distinct but closely approximated inflor- 
escences. (Satter (2) ; 'see Ruhland (i), pp. 204, 205.) 

The Sporophyte 

The first (basal) w^all in the fertilised ovum divides it into 
an upper and low^er cell, as in Sphagmmi and Andrecca, and the 
next divisions correspond closely to those in the latter. In both 
cells a wall is formed intersecting the basal wall, but not at 
right angles. This is especially the case in the upper cell where 
a second wall strikes the first one nearly at right angles, and 
establishes the two-sided apical cell by which the embryo grows 
for a long time. In the lower cell the divisions are somewhat 
less regular, but here also it is not uncommon to find a some- 
what similar state of affairs, so that the embryo may be said to 
have two growing points, although the lower end shows neither 
such regular nor so active growth as the upper one. In the lat- 
ter the divisions follow each other with almost mathematical 
precision. There seems to be no rule as to how many segments 
are cut off from the apical cell before it ceases to function as 
such, but there are more than in Andrecca, and the embryo 
soon becomes extremely elongated. A series of transverse 
sections of the young sporogonium shows very beautifully the 
succession of the first walls in the young segments. In a sec- 
tion just below the apex (Fig. 107, A), each segment is seen to 



204 



MOSSES AND FERNS 



CHAP. 



.■ ( .: -. . 






Fig. io6. — Funaria hys:rometrica. Development of the embryo. A, Optical section 
of a very young embryo; B, C, surface view and optical section of an older one, 
X6oo; C, D, longitudinal sections of the apex of older embryos, X6oo; en, endo- 
thecium; am, amphithecium. 



VI. 



THE BRYALES 



205 



be first divided by a median wall into two equal cells. In 
Fiinaria usually the next division wall is periclinal, and at once 
separates endothecium and amphithecium. In most other 
Bryineae that have been examined, however, and this may also 
occur in Fimaria (see Fig. 107, A), the second walls formed in 
the young segments are anticlinal, and it is not until the third 
set of walls is formed that the separation of endothecium and 
amphithecium is complete. The next divisions (Fig. 107, C), 
are in the amphithecium, and separate it into two layers. In 
the endothecium a series of walls is next formed, almost exactly 
repeating the first divisions in the original segment (Figs. D, 




N 



Fig. 107. — Five transverse sections of a young embryo of F. hygrometrica. A, Just 
below the apex, the others successively lower down; en, endothecium, X450' . 



E), and transforming it into a group of four central cells and 
eight peripheral ones. Each of the latter divides twice by in- 
tersecting walls, so that a group of about sixteen cells (Fig. 
108, A), occupies the middle of the endothecium. The eight 
peripheral cells divide by radial walls, after which each of these 
cells is divided by a periclinal wall into an outer and an inner 
cell (Fig. 108, B), and the outer cells divide rapidly by radial 
walls and form the archesporium. The single layer of cells 
immediately within, and therefore sister cells of the primary 
archesporial ones, is the inner spore-sac. 

The account of the development of the endothecium here 
given differs slightly from the account of Kienitz-Gerloff (2), 



206 



MOSSES AND FERNS 



CHAP. 



It was found first that there was not the absolute constancy in 
the number of cells given by him; thus in Fig. io8, A there 
are only fourteen cells in the inner part of the endothecium, 
and although there are sixteen cells in the outer row their 
position is not perfectly symmetrical. Again the periclinal 
division of the cells of the inner spore-sac takes place later than 
he states is the case. 

In the eight primary cells of the amphithecium there first 
arise periclinal walls that divide each cell into an inner small 
cell in contact with the endothecium, and an outer larger one. 




Fig. 108.— Three transverse sections of an older sporogonium of F, h^grometrica, X400; 

ar, archesporium; t, intercellular spaces. 



This first division separates the wall of the capsule from the 
outer spore-sac. The latter next divides by radial and trans- 
verse walls, and later by periclinal walls into two layers (Fig. 
108). Almost coincident with the latter, the rows of cells 
lying immediately outside it show a very characteristic appear- 
ance. They cease to divide, and with the rapid growth in 
diameter of the capsule become much extended both vertically 
and laterally, but are compressed radially. It is between these 
cells and the spore-sac that the characteristic air-space found 
in the capsule is formed. This is first evident shortly after 
the enlargement of the base of the capsule begins. The devel- 



VI. THE BRYALES 207 

opment can be very easily followed in longitndinal sections 
made at this stage. The formation of the space begins at the 
base of the capsule and proceeds toward the top. Hie line of 
cells bordering on the spore-sac is very easily followed, owing 
to their being so much larger than the neighlxjuring ones. As 
this is followed down, it is found that at the base of the capsule 
the cells are separated by large intercellular spaces, which be- 
come less marked toward the apex. With the rapid enlarge- 
ment of the capsule these spaces become very large, and sec- 
tions made a little later show that during this process the cells 
remain in contact at certain points, and form short filaments 
that extend across the space and unite the wall of the capsule 
with the outer spore-sac. At the base of the capsule the for- 
mation of intercellular spaces is not confined to the single layer 
of cells but involves the whole central mass of tissue, which be- 
comes thus transformed into a bundle of filaments connecting 
the columella with the basal part (apophysis) of the capsule. 
The innermost of the two layers of cells between the arche- 
sporium and the air-space finally undergoes a second periclinal 
division, and in the full-grown sporogonium the archesporium 
is bounded on the outside by three layers of cells. 

The differentiation into seta and capsule takes place late 
in Fimaria, and the first indication of this is the enlargement 
of a zone between the two, forming the apophysis, which at 
this stage (Fig. 109), is much greater in diameter than the 
upper part of the capsule. Sections through the apophysis 
and seta show a less regular arrangement of the cells than in 
the sporiferous part of the capsule, but the general order of 
cell-succession is the same, except for the formation of the 
archesporium. Almost as soon as the capsule is recognisable, 
the first indication of the operculum or lid becomes evident. 
About half-way between the extreme apex of the sporogonium 
and the top of the apophysis, a shallow^ depression is noticed 
extending completely round the capsule and separating the 
sharply conical apex from the part below. An examination of 
a longitudinal section at this point shows that at the point of 
separation the epidermal cells of the opercular portion are much 
narrower than those immediately below. Examining the tis- 
sues farther in, the archesporium is seen to extend only to a 
point opposite the base of the operculum, and the same is true 
of the row of large cells where the air-space is formed. If a 




Fig. 109. — Funaria hygrometrica. A, Longitudinal section of a sporogonium showing 
the first differentiation of its parts, X about 96; B, the upper part of the same, 
X600; r marks the limits of the theca and operculum; C, basal part of the cap- 
sule of the same, X600. The intercellular spaces are beginning to form; ar, 
archesporium; col, columella. 



VI. 



THE BRYALES 



200 



similar section is made through an older capsule (Fig. no), 
it is evident at once that the enlargement takes place mainly 
below the junction of the operculum, and there is also a similar 
but less pronounced increase in diameter in the operculum itself ; 
but there is a narrow zone at the junction of the operculum and 
capsule, where the epidermal cells increase but little in depth, 
while those above this point become very much larger and pro- 
ject beyond them. This narrow zone of cells marks the point 
where when ripe the operculum becomes detached. The latter, 




Fig. ho. — Longitudinal section of an older capsule of F. hygrometrica; i, intercellular 
spaces; sp, archesporium; r, cells between operculum and theca, XS^S- 



Up to the time the sporogonium is ripe, is composed of a close 
tissue without any intercellular spaces. The epidermal cells, 
seen from the surface, are seen to be arranged in spiral rows 
running from the base to the apex. Its central part is made up 
of large thin-walled parenchyma, continuous with the tissue of 
the columella. The archesporium, therefore, is not continuous 
over the top of the columella, as in Sphagnum and Andrecea, 
but is cylindrical. The archesporium forms simply a single 
layer of small cells, and occupies a very small part of the sporo- 
14 



210 



MOSSES AND FERNS 



CHAP. 



gonium, much less, relatively, than in any of the forms hitherto 
described. Before the final division of the spores it divides 
more or less completely into two layers. The cells resulting 
from this last division are the spore mother cells, which separate 
soon after their formation and lie free in the space betw^een the 
inner and outer spore-sacs, where each one divides into four 
tetrahedral spores. 

In the operculum, as the capsule approaches maturity, the 
differentiation of annulus and peristome takes place. The 
annulus consists of five or six rows of cells that occupy the 



B 





Fig. III. — A, Longitudinal sections of a nearly ripe capsule of F. hygrometrica, X260; 
per, peristome; r, annulus; t, thickened cells forming the margin of the theca; B, 
the sporogenous cells shortly before the final divisions; i, inner; 0, outer spore- 
sac, X525- 



periphery of the broadest part of the operculum. The upper 
rows of cells are very much compressed vertically, but are 
greatly extended radially and have their walls thicker than those 
of the neighbouring cells. These thickened annulus cells form 
the rim of the loosened operculum. The two lower rows of 
annulus cells — the annulus proper — have thin walls and finally 
become extremely turgescent. It is the destruction of these 



VI. 



THE BRYALES 



211 



cells, when the capsule is ripe, that effects the separation be- 
tween the operculum and theca. 

The peristome arises from the fifth layer of cells from the 
outside of the operculum. If a median longitudinal section of 
a nearly ripe capsule is examined, the row of cells belonging 
to this layer (Fig. iii, per), is at once seen to have the outer 
walls strongly thickened, and this thickening extends for a 
short distance along the transverse walls. The inner walls of 
the cells also show a slight increase in thickness, but much less 
marked than the outer ones. A similar thickenhig of the cell 
walls occurs also in about three rows of cells which run from 




S. "^- 

Fig. 112. — Longitudinal section of a fully-developed sporogonium of Funaria hygro- 
metrica, X about 40; s, seta: a, apophysis; sp, spores; col, columella; r, annulus; 
o, operculum. 



the outside of the capsule to the base of the peristome, and form 
the rim of the ''theca" or urn. 

The epidermis of the whole capsule has its outer walls very 
much thickened, and upon the apophysis are found stomata 
quite similar to those found upon the sporogonium of Antho- 
ceros or upon the leaves of vascular plants. Haberlandt ( (4), 
p. 464), showed that while the form of the fully-developed 
stoma in Funaria differs from that of most vascular plants, 
this difference is secondary, and that in its earlier stages no 
difference exists. This can be easily verified, and with little 
difficulty all the different stages found. The young stoma 
(Fig. 113), has the division wall extending its whole length. 



212 



MOSSES AND FERNS 



CHAP. 



as is the case in stomata of the ordinary form. As the stoma 




Fig. 113.— ~Funaria hygrometrica. A, Young; B, older stoma, from the base of the 

capsule; C, vertical section, X360. 

grows larger, however, the median wall does not grow as fast 
as the lateral walls, and a space is left between its extremities, 

B, 

A. 





Fig. 114. — Funaria hygrometrica. A, Part of the peristome; o, an outer tooth; t, one 
of the inner teeth, X85; B, section of the seta, X260; C, cross-section of upper 
•part of calyptra, X525, 



SO that the two guard cells have their cavities thrown into 
communication, and the division wall forms a cellulose plate 



vr. THE BRYALES 213 

extending from the lower to the upper surface of the stoma, 
but with its ends quite free. The formation of the pore by 
the sphtting of the middle lamella of the division wall takes 
place in the ordinary way. Later the walls of the epidermal 
cells become very thick and show a distinct striation (Fig. 
113). By the formation of the stomata the green assimilat- 
ing tissue of the apophysis and central part of the capsule is 
put into direct communication with the external atmosphere. 

The lower part of the seta grows downward and penetrates 
the top of the stem of the gametophyte, from which, of course, 
it derives a portion of its sustenance. The centre of the seta 
is traversed by a well-marked central cylinder, whose inner 
cells are small and thin-walled, and are mainly concerned in 
conducting water ; immediately outside of this is a circle of 
thick-walled brown cells (leptome of Haberlandt), and the 
rest of the seta is made up of nearly similar thick-walled cells 
which grow smaller toward the periphery. 

At maturity, as the supply of w^ater is cut off from below, 
the capsule dries up, and all the delicate parenchyma compos- 
ing the columella and inner part of the operculum, as well as 
that between the spore-sac and the epidermis of the theca, com- 
pletely collapses, leaving little except the spores themselves, and 
the firm cell wells of the peristome, and the cells connecting 
the latter with the wall of the capsule. By the breaking down 
of the unthickened lateral and transverse walls of the peri- 
stomial cells, the outer and inner thickened walls are separated 
and form the two rows of membranaceous teeth that surround 
the mouth of the urn^ (Fig. 114). By the drying up of the 
thin-walled cells between the annulus and the margin of the 
theca the operculum is loosened and is very easily separated. 
The teeth of the peristome are extremely hygroscopic, and 
probably assist in lifting off the operculum as well as removing 
the spores from the urn. When wet they bend inward, extend- 
ing into the cavity of the urn. As they dry they straighten 
out and lift the spores out. The marked hygroscopic move- 
ments of the seta also are no doubt connected with the dissem- 
ination of the spores. 

The calyptra in the Bryales is very large and is carried 
up on the top of the sporogonium in the form of a conspicuous 
membranaceous cap. As in other forms it is the venter alone 
that shows secondary growth. In Fimaria it increases very 



214 MOSSES AND FERNS chap. 

much in diameter at the base, where it is widened out like a 
bell, and far exceeds in diameter the enclosed embryo. Above 
it is narrow and lies close to the embryo. After a time the 
embryo grows more rapidly in length than the calyptra, which 
then is torn away by a circular rent about its base, and is 
raised on top of the elongating sporogonium. The lower por- 
tion remains delicate and nearly colourless, but the upper part 
has its cells thick-walled and dark-brown in colour (Fig. 114, 
C). Tipping the whole is the persistent dark-brown neck of 
the archegonium. 

Classification of the Bryales 

CleistocarpcB 

The simplest of the Bryales are the CleistocarpcB or those 
in which there is no operculum developed, and in consequence 
the capsule opens irregularly. If Archidhtm is removed from 
this group the simplest form known is Ephemerum. In this 
genus, from a highly-developed filamentous protonema are pro- 
duced the extremely reduced gametophores. According to 
Miiller, (2) who has studied the life-history of this genus, 
both male and female branches arise from the same protonema, 
and are only distinguishable by the smaller size of the former. 
The axis of the branch is scarcely at all elongated, and the leaves 
therefore appear close together. The sexual organs corre- 
spond closely in origin and structure to the other Bryales. The 
development of the sporogonium in its early phases is also the 
same, and the differences only appear at a late stage. The 
separation of endothecium and amphithecium is apparently ex- 
actly the same as in other Bryales, and from the former is de- 
rived the archesporium, which like that of Funaria has the form 
of a hollow cylinder through which the columella passes. Be- 
tween, the outer spore-sac and the wall of the sporogonium an 
intercellular space is also formed, but the separation of the cells 
is complete, and there are no filaments connecting the spore-sac 
and the sporogonium wall as in Funaria. The cells of the 
archesporium are few in number and correspondingly large 
(Fig 115, E), and before the division into the spores takes 
place all the central tissue of the columella is absorbed, and 
the spore mother cells occupy the whole central space, where 
the division of the spores is completed, and at maturity the 



VI. 



THE BRYALES 



21 




Fig. 115. — A, Longitudinal section of the young sporogonium of Pleuridium subulatum, 
X8o; B, part of the same, X600; sp, archesporium; C, young embryo of Phasciim 
cuspidatum, optical section, X17S; D, cross-section of an older embryo of the 
same, X350; sp, archesporium; E, longitudinal section of the central part of the 
young sporogonium of Ephemerum pliascoides, X350; sp, archesporium. C, D, 
after Kienitz-Gerloff ; E, after MuUer. 



2l6 



MOSSES AND FERNS 



CHAP. 



whole of the capsule is filled with the large spores, and no trace 
of the columella remains. 

Nanomitrium (Goebel (22), p. 374), closely resembles 
Ephemerum in the development of the sporophyte. 

The highest members of the Cleistocarpse, such as Phascum 
and Pleiiridhim (Fig. 116), approach very closely in structure 
the stegocarpous Bryales. In these the gametophore is much 
better developed than in Ephemerum, and the protonema not 
so conspicuous. The leaves also frequently have a well- 
developed midrib which is wanting in the leaves of Ephemerum. 
Kienitz-Gerlofif (2) has carefully studied the embryogeny 
of Phascum cuspidatum, and except in a few minor details it 

corresponds verv closely to that of 
Funaria, except, of course, as re- 
gards the operculum and peristome, 
which are absent. In Phascum, 
however, the archesporium is dif- 
ferentiated earlier than in Funaria. 
In each of the four primary cells of 
the endothecium, as seen in trans- 
verse section, a periclinal wall 
arises which at once separates the 
archesporium from the columella 
(Fig. 115, D). The outer spore- 
sac has but two lavers of cells, and 
the capsule wall three, and between 
them the large lacuna is formed as 
in Funaria; but in Phascum as in 
Ephemerum, the separation of the 
cells is complete. In the seta a 
slightly-developed central cylinder of conducting tissue is de- 
veloped, derived, as in Funaria, from the endothecium, but in 
Phascum it is much less conspicuous. Pleuridium (Fig. 
115, A) in its later stages corresponds exactly to Phascum, ex- 
cept that the capsule is more slender. In both of these genera 
the seta remains short, but is perfectly evident. Whether the 
absence of a distinct operculum in the cleistocarpous Mosses is 
a primitive condition, or whether they are reduced forms, it is 
impossible to determine positively from a study of their em- 
bryogeny. 




Fig. 116. — Pleuridium suhulatum, 
X20. 



VI. THE BRYALES 217 

Stegocarpco 

Very much the larger number of Mosses belong to this 
group, which is primarily distinguished from the foregoing by 
the presence of an operculum. Of course among the 7000 or 
more species belonging here there are many differences in struc- 
ture ; but these are mainly of minor importance morphologically, 
and only the more important differences can be considered here. 

As we have already seen, there is great uniformity in the 
growth of the stem, which, with the single exception of Fis- 
sidens, has always a three-sided pyramidal apical cell. In 
Fissidens this is replaced by a two-sided one, but even here it 
has been found (Goebel (8), p. 371) that the underground 




Fig. 117. — Cyathophorum pennatum, showing three rows of leaves; sp, sporophytes, 

stems have a three-sided initial cell, which is gradually replaced 
by the two-sided one after the apex of the shoot appears above 
ground. In Fissidens the leaves are arranged in two rows cor- 
responding to the two sets of segments, and are sharply folded,, 
so that the margins of the leaf are covered over by those of the 
next older ones, leaving only the apex free. A similar arrange- 
ment is found in the genus Bryoziphion (Enstichia), but here 
there is a three-sided apical cell, and the two-ranked arrange- 
ment of the leaves is secondary. In Cyathophorum (Fig. 117), 
there are two row^s of large dorsal leaves and a row of much 



2i8 MOSSES AND FERNS chap. 

smaller ventral ones, so that the plant resembles very closely a 
foliose Liverwort. The curious genus Schistostega shows also 
a two-ranked arrangement of the leaves of the sterile branches, 
but here they are placed vertically and the bases connivent, so 
that the effect of the whole is that of a pinnatifid leaf. The 
fertile branches, however, have the leaves spirally arranged, 
and in the sterile ones the three-sided apical cell is found. The 
leaves, with few exceptions, e. g., Fontinalis, have a well- 
marked midrib, and the lamina is single-layered. Leucobryum 
(Fig. 121, A) has leaves made up of two or three layers of 
cells, large hyaline ones, somewhat as in Sphagnum, and small 
green cells. The hyaline cells, as in Sphagnum, have round 
holes in the walls, but no thickenings. The midrib may be 
narrow, as in Funaria, or it may occupy nearly the whole 
breadth of the leaf, as in the Polytrichacese, where, owing to 
the almost complete suppression of the lamina, secondary ver- 
tical plates of green cells are formed (Fig. 121, B). 

The one-third divergence of the leaves found in Fontinalis^ 
is replaced in most other genera by a larger divergence. 
(Goebel (8) ). Thus in Funaria hygrometrica it is f ; in Poly- 
trichum commune ^; in P. formosum if. 

As the archegonia are borne upon lateral branches, or upon 
the main axis, the stegocarpous Bryinese are frequently divided 
into two main divisions, the Pleurocarpse and the Acrocarpae, 
which are in turn divided into a number of subdivisions or 
families. How far the division into acrocarpous and pleuro- 
carpous forms is a natural one may be doubted, as probably the 
latter are secondary, and it is quite conceivable that different 
families of pleurocarpous forms may have originated inde- 
pendently from acrocarpous ones. 

The simplest of the stegocarpous Mosses, while having the 
operculum well marked, have no peristome. Thus the genus 
Gymnostomum has no peristome at all, and in an allied genus, 
Hymenostomwn, it is represented by a thin membrane covering 
the top of the columella. In nearly related genera, however, 
e. g., Weisia, a genuine peristome is present. 

The Tetraphidese, represented by the genus Tetraphis 
(Georgia) (Fig. 118), are interesting as showing the possible 
origin of the peristome, as well as some other interesting points 

^ This seems to be strictly the case only in the smaller branches ; in the 
larges axes the leaves are not exactly in three rows. 



w. 



THE BRYALES 



±1^ 



of structure. Tetraphis pellucida is a small Moss, which at 
the apex of its vegetative branches bears peculiar receptacles 
containing multicellular gemmae of a very characteristic form. 
The leaves that form the receptacle are smaller than the stem 
leaves, and closely set so as to form a sort of cup in which the 
gemmae are produced in large numbers. These arise as slender 
multicellular hairs, the end cell of which enlarges and forms a 
disc, at first one-layered, but later, by the walls parallel to the 
broad surfaces, becoming thicker in the middle, and lenticular 




Fig. ii8. — Tetraphis pellucida. A, Plant with gemmae, X6; B, upper part of the 
same, X50; C, young gemma, X600; D, a fully-developed gemma, X300. 



in form. The arrangement of the cells in the young gemmae 
looks as if the growth of the bud was due to a two-sided apical 
cell (Fig. 118, C), but this point was not positively determined. 
These gemmae give rise to a protonema of a peculiar form, from 
which in the usual way the leafy stems develop. The proto- 
nemal filaments grow into flat thalloid expansions that recall 
those of Sphagnum and Andrecua. 



220 



MOSSES AND FERNS 



CHAP, 



The sporogonium of Tetraphis has a peristome of pecuHar 
structure, and not strictly comparable to that of any of the 
other Mosses. After the operculum falls off the tissue lying 
beneath splits into four pointed teeth, which, however, are not, 
as in Funaria, composed simply of the cell walls, but are masses 
of tissue. 

All the other higher Bryales, with the exception of the 
Polytrichacese, have the peristome of essentially the same struc- 
ture as that described for Funaria. Sometimes the teeth do not 
separate but remain as a continuous membrane, e. g., the inner 




f'AA\f/fMf 



•• Sa • n o   « 





Fig. 119. — A, Barhula fallax, upper part of the capsule, showing the slender twisted 
peristome teeth X about 20. B, Fontiualis antipyretica, showing double 
peristome (after Schimper). C, Polytrichum commune, peristome and epiphragma 
X8. D, P. commune, ripe capsule; i, with, 2, without the calyptra X3. 



peristome of Buxhaumia, or a perforated membrane, as in Fon- 
tinalis (Fig. 119, B). 

The base of the capsule, or apophysis, which Haberlandt 
(4) has shown to be the principal assimilative part of the sporo^: 
gonium, and which alone is provided with stomata, sometimes 
becomes very large, and in the genus Splachnum (Vaizy (i)) 
especially forms a largely-developed expanded body, which, 
must be looked upon as a specially-developed assimilating ap-: 
paratus. . - ;orL 



VI. 



THE BRYALES 



221 



Undoubtedly the Polytrichacese represent the highest stage 
of development among the Musci. This is true both in regard 
to the gametophore and the sporogonium. The former reaches 
in some species, e. g., P. commune, a length of 20 centimetres 
and sometimes more. The stem is usually angular and the 
closely-set leaves thick and rigid. The numerous rhizoids are 
often closely twisted together and form cable-like strands. The 
structure of the leaves is very characteristic, and differs very 
much from that of the simpler type found in Funaria. 



G 




Fig. 120. — Dawsonia superba. A, upper part of female plant bearing a sporogonium, 
Xi; B, a leaf, slightly enlarged; C, section of leaf, X about 70; D, part of the 
same more highly magnified; E, two views of the capsule, Xi^. 



In the Polytrichacese (Fig. 121) the midrib of the leaf is 
very broad and only at the extreme margin of the leaf is the 
lamina developed at all. A cross-section of the leaf shows that 
the midrib is greatly thickened in the centre, and gradually 
merges into the rudimentary lamina. In Dazvsonia (Fig. 120), 
the leaf is almost flat, in Polytrichiim (Fig. 121), usually 
more or less incurved at the margin. 

The outer, or dorsal, surface of the leaf is covered with a 
well marked epidermis, whose outer cell-walls are strongly 



222 MOSSES AND FERNS chap. 

thickened, and have a conspicuous cuticle. Within this epi- 
dermis are closely set, small sclerenchymatous elongated cells, 
among which are found more or less definite rows of large, 
thin-walled elements, strongly suggesting the tracheary tissue 
of the vascular plants, and without much question, true water- 
conducting structures. From the inner ventral surface there 
arise numerous parallel, thin, vertical laminae (cl.) composed 
of green cells. These extend nearly the whole length of the 
leaves and in section appear as rows of short cells, the outer- 
most ones being somewhat enlarged. 

The axis of the shoot in the Polytrichaceae shows a decidedly 
complex structure and many reach a relatively large size. 
Thus in Dazvsonia snperba (Figs. 120, 122) it is about 1.5 mm. 
in diameter, and forms an erect, densely leafy shoot 40 to 50 
centimetres in height. The cross-section of the shoot in the 
latter species (Fig. 122) is triangular in outline. Within the 
firm epidermis there are several layers of somewhat similar, 
but more compact cells, which like the epidermal cells are thick- 
walled, and dark coloured. This compact hypodermal tissue 
passes somewhat gradually into a colourless, parenchymatous 
ground-tissue, which makes up the bulk of the shoot-axis. 
There is a very conspicuous central cylinder composed of two 
tissue-elements — small, dark-colored sclerenchyma or fibrous 
tissue, especially compact toward the centre of the cylinder ; and 
very much larger, thin-walled cells, appearing almost destitute 
of protoplasmic contents, and closely resembling the vessels of 
true vascular plants, and like them, no doubt, true water-con- 
ducting organs. Traversing the ground tissue are slender 
strands of elongated cells — leaf-traces, which are structurally 
like the central cylinder of the shoot, but with the water- 
conducting cells less conspicuous. Most of the cells in the 
stem of Dawsonia, except the large tracheary cells of the central 
cylinder, contain starch, which it is stated by Goebel (8) is not 
abundant in the tissues of Polytrichum, where its place is taken 
largely by oil. Starch has been noted in Polytrichum in the 
outer cells of the stem and in the leaf-traces. 

The leaf-traces, or continuation of the central tissue of the 
midribs of the leaves, bend down into the stem, and finally 
unite with the axial cylinder of the latter, in a manner 
quite analogous to that found in the stems of many vascular 
plants. 



VI. 



THE BRYALES 



223 




Bastit ((i), p. 295), 
who has made a compar- 
ative study of the subter- 
ranean and aerial stems of 
P. jimiperiniim, divides 
the outer tissue of the lat- 
ter into epidermis, hypo- 
derma, and cortex. In 
the subterranean stems he 
finds the construction 
quite different from that 
of the leafv branches. 
The section of the former 
is triangular, and its epi- 
dermis provided with 
hairs which are absent 
from the epidermis of the 
aerial parts. Rudimen- 
tary scales, arranged in 
three rows, are present, 
and corresponding to 
these are strands of tissue 
that represent the leaf- 
traces of the aerial stems. 
The central cylinder is 
much larger relatively 
than in the leafy branches, 
and its cross-section is not 
continuous, but is inter- 
rupted by three "pericyclic 
sectors," composed of 
cells whose walls are but 
little thickened. The 
point of each sector is at 
the periphery of the me- 
dulla, or central cylinder, 
and the broad end toward 
the centre. As might be 
expected, intermediate con- 
ditions are found where 
the rhizome begins to grow upward to form a leafy branch. 




Fig. 121. — A, Transverse section of the leaf of 
Leucohryum; B, similar section of the leaf of 
Polytrichum commune; cl, chlorophyll-bear- 
ing cells (after Goebel). 



224 



MOSSES AND FERNS 



CHAP. 



The male inflorescence of the Polytrichaceae is especially 
conspicuous, as the leaves immediately surrounding the anther- 
idia are different both in form and colour from those of the 
stem. They are broad and membranaceous, and more or less 
distinctly reddish in colour. A well-known peculiarity of 
these forms is the fact that the growth of the stem is not 
stopped by the formation of antheridia, but after the latter have 
all been formed the axis resumes its growth and assumes the 
character of an ordinary leafy shoot. This, of course, indi- 
cates that, unlike most of the Mosses, the apical cell does not 
become transformed into an antheridium, and the researches of 




Fig. 122. — Dawsonia superba. A, Transverse section of the stem, X3S; B, part of the 
central cylinder, showing water-conducting elements, t, X200; C, outer tissues 
of the stem, X200. 



Hofmeister (2), Leitgeb (9), and Goebel (7) have shown 
that this is the case. The antheridia form groups at the base 
of each leaf of the inflorescence, and Leitgeb thinks it probable 
that each group represents a branch, i. e., the inflorescence is a 
compound structure, and not directly comparable to the simple 
male inflorescence of Funaria. The sporogonium in Poly- 
trichum has a large intercellular space between the inner spore- 
sac and columella as well as the one outside the outer spore-sac. 
In both cases the space is traversed by the conferva-like green 
filaments found in the other stegocarpous Mosses. The apoph- 
ysis is well developed, especially in Polytrichum, and the 



VI. 



THE BRYALES 



225 



calyptra very large and covered with a dense growth of hairs 
(Fig. 119, D). 

The structure of the peristome in the Polytrichaceae is 
entirely different from that of tlie other Mosses. It is com- 
posed of bundles of thickened fibrous cells arranged in crescent 
form, the ends of the crescent pointing up, and united with the 
adjacent end of the bundle next it. The tops of the teeth thus 
formed are connected by a layer of cells stretching across the 
opening like the head of a drum. This membrane is known 
technically as the ''Epiphragm" (Fig. 119, C). 

The Buxbaumiace^ 

The last group of Mosses to be considered is the very 
peculiar one of the Buxbaumiaceae. In these Mosses the 





Pig. 123. — A, Protonema of Buxbaumia indusiata, with the anthreidial shoot, X175; 
B, antheridium, seen in optical section ; C, sporophyte of B. sp., X4' (A, B, after Goebel.) 



gametophyte is extraordinarily reduced, although the sporo- 
gonium is large and well developed. So simple is the sexual 
plant, that Goebel (i6) has concluded that these ought to be 
taken away from the rest of the Mosses, and removed to a dis- 
tinct order. According to Goebel's account, the antheridia, 
which are long stalked, are borne directly upon the protonema, 
and subtended by a single colourless bract (Fig. 123). The 
female branches are also very rudimentary, but less so than the 
male. On the strength of the extreme simplicity of these. 
Goebel thinks that Biixhaumia is a primitive form allied to some 
alga-like progenitor of the Mosses. There are, however, two 
very strong objections to this. First the sporogonium, which 
15 



226 MOSSES AND FERNS chap. 

is extremely large, and complicated in structure, and essentially 
like that of the other stegocarpous Mosses; secondly, Bux- 
haumia has been shown by Haberlandt ((4), p. 480) to be 
distinctly suprophytic in its habits, and the extreme reduction 
of the assimilative tissue of the gametophyte is quite readily 
explicable from this cause. 

Fossil Muscine^ 

The remains of Muscinese in a fossil condition are exceed- 
ingly scanty ; so much so indeed as to practically throw no light 
upon the question of their origin and affinities, as nearly all of 
the forms discovered belong to the later formations, and are 
either identical with living species or closely allied forms. No 
doubt the great delicacy of the tissues of most of them, espe- 
cially the Hepaticse, accounts in great measure for their absence 
from the earlier geological formations. 

The Affinities of the Musci 

It is perfectly evident that the Mosses as a whole form a 
very clearly defined class, and that their relationship with other 
forms is at best a somewhat remote one. Sphagnum, however, 
certainly shows significant peculiarities that point to a connec- 
tion between this genus, at least, and the Hepaticse. It will be 
remembered that the protonema of Sphagnum is a large flat 
thallus, and not filamentous, as in most Bryales. It it note- 
worthy, however, that from the margin of this flat thallus later 
filamentous branches grow out which are apparently identical 
in structure with the ordinary protonemal filaments of the 
Bryales. In Andrecea similar flat thalloid protonemata occur, 
but not so largely developed as in Sphagnum, and finally in 
Tetraphis a similar condition of affairs is met with. As this 
occurs only among the lower members of the Moss series, the 
question naturally arises, does this have any phylogenetic mean- 
ing? While it is impossible to answer this question positively, 
it at any rate seems probable that it has a significance, and 
means that the protonema has been derived from a thalloid 
form related to some thallose Liverwort, and that by the sup- 
pression of the thalloid portion, as the leafy gametophore 
became more and more prominent, the filamentous branches, 



VI. THE BRYALES 227 

which at first were mere appendages of the thalkis, finally came 
to be all that was left of it. The view of Goebel and others that 
the filamentous form of the protonema is the primitive one, and 
indicates an origin from alga-like ffjrms, might be maintained 
if the question were concerned simply with the prrjtonema ; but 
when the structure of the sexual organs, esjjecially the arche- 
gonium, is considered, and the development of the sporophyte, 
the difficulty of homologising these with the corresponding 
parts in any known Alga is apparent, while on the other hanrl 
the resemblance between them and those of the IlepaticcC is 
obvious. It is quite probable that the development of the fila- 
mentous protonema is a provision for the production of a 
greater number of gametophoric branches. 

As to which group of the Hepaticse comes the nearest to 
the Mosses, the answer is not doubtful. The remarkable simi- 
larity in the development and structure of the sporogonium 
of Sphagnum and the Anthocerotes leaves no room for doubt 
that as far as Sphagnum is concerned, the latter come nearest 
among existing forms to the ancestors of Sphagnujn. Of 
course this does not assume a direct connection between 
Sphagnum and any known form among the Anthocerotes. 
There are too many essential differences between the two to 
allow any such assumption : but that the two groups have come 
from a common stock is not impossible, and the structure of the 
capsule in Sphagnum points to some form which like Antho- 
ceros had a highly-developed assimilative system. This is 
indicated by the presence of stomata, which, aUhough function- 
less, probably were once perfect, and make it likely that with 
the great increase in the development of the gametophyte the 
sporophyte has lost to some extent its assimilative functions 
which have been assumed by the gametophyte. 

AndrecBa, both in regard to the gametophyte and the sporo- 
phyte, is in many ways intermediate between Sphagnum and the 
other Mosses. The resemblance in the dehiscence of the 
sporogonium to that of the Jungermanniaceae is probably acci- 
dental. It may perhaps be equally well compared to the split- 
ting of the upper part of the capsule into four parts, in Tctra- 
phis, although in the latter it is the inner tissue and not the 
epidermis which is thus divided. 

If this latter suggestion proves to be true, then there would 
be a direct connection of Andrecca with the stegocarpous 



228 MOSSES AND FERNS ciiap. 

Bryales, and not through the cleistocarpous forms. These 
latter would then all have to be considered as degraded forms 
derived from a stegocarpous type, unless, with Leitgeb, we 
consider them as a distinct line of development leading up to 
the higher Bryales, entirely independent of the Sphagnaceae, 
and with Archidium and Ephemerum as the simplest forms. 
His comparison of these forms with Notothylas, however, can- 
not be maintained with our present knowledge of that genus, 
and more evidence is needed before his view can be accepted; 
but the possibility of some such explanation of the cleistocarp- 
ous Bryales must be borne in mind in trying to assign them 
their place in the system. 

The objections to considering Buxbaumia a primitive type 
have been already given, and it is not necessary to repeat them. 



CHAPTER VII 

THE PTERIDOPHYTA-FILICINE^-OPHIOGLOSSACE^ 

In tracing the evolution of the Bryophytes from the lowest to 
the highest types the gradual increase in the importance of the 
second generation, the sporophyte, is very manifest. This may 
or may not be accompanied by a corresponding development of 
the gametophyte. In the line of development represented by 
the higher Mosses, in a general way the two have been parallel, 
and the most highly differentiated gametophyte bears the most 
complicated sporophyte, as may be seen in Polytricluim, for 
example; but in the Hepatic^e this is not the case, and among 
the Anthocerotes much the most highly organised sporophyte, 
that of Anthoceros, is produced by a very simple gametophyte. 

In this evolution of the sporophyte, it approaches a condition 
where it is self-supporting, but in no case does it become abso- 
lutely so. A special assimilative tissue, it is true, is developed, 
and in some of the true Mosses, such as Splachnum, this goes so 
far that a special organ, the apophysis, is formed; but, as we 
have seen, the sporogonium is dependent for its supply of water 
and nitrogenous food upon the gametophyte, with which it 
remains intimately associated, and upon which it lives as a 
parasite. 

The type of structure found in the gametophyte of the 
Muscinese seems to be imperfectly fitted for a strictly terres- 
trial life. The gametophyte of all Archegoniates is more or less 
amphibious. Free water is essential for the act of fecundation, 
and the gametophyte seems never to have solved satisfactorily 
the problem of an adequate water supply, except by returning 

to the aquatic condition. 

229 



230 MOSSES AND FERNS chap. 

Many Bryophytes can exist only in damp, shady localities, 
and those which have adapted themselves to a xerophytic habit, 
have acquired the power of becoming completely dried up with- 
out being killed, reviving promptly when supplied with water, 
but remaining completely dormant during the period of 
drought. These plants do not depend upon their rhizoids for 
absorbing water, but, like Algae, can absorb water at all points 
of their surface. Where the plant depends largely upon the 
rhizoids for water absorption, as in the Marchantiacese, the 
plant is a flat, prostrate thallus, which offers a large surface for 
the development of the rhizoids. In the upright stems of the 
larger Mosses, the rhizoids are multicellular, and sometimes 
twisted into root-like strands, which are of relatively large size, 
and are undoubtedly efficient organs for water-absorption. 
Still it is evident that even such strands of multicellular rhizoids 
w^ould not suffice for providing the water necessary to make 
good the loss by transpiration in a large terrestrial plant. 
It is this failure to develop an adequate root system which prob- 
ably explains the fact that no Bryophyte has attained the dignity 
of a successful upright terrestrial plant. 

Among the Pteridophytes the gametophyte is equally in- 
capable of a strictly terrestrial existence; but in these plants, 
the sporophyte, developing still further along lines indicated in 
many Bryophytes, has finally attained to the condition of an 
independent plant. It may be conjectured that from part of 
the foot, the absorbent organ of the embryo in the bryophytic 
sporophyte, there was developed a root, with a permanent grow- 
ing point, and capable of indefinite growth in length. This, 
penetrating through the tissues of the gametophyte, put the 
sporophyte into direct communication with the water in the 
earth, and thus completely emancipated it from its former status 
of dependence upon the gametophyte. 

The true root differs essentially from the rhizoids in being 
a massive organ capable of indefinite growth and division, 
which can thus keep pace in its development with the increasing 
size and complexity of the sporophyte. The latter from this 
time assumes more and more the principal role in the life- 
history of the organism, while the gametophyte becomes corre- 
spondingly reduced. With the development of an independent 
sporophyte, there appeared a plant adapted from the first 
to a terrestrial existence and not a modification of an originally 



VII PTERIDOPHYTA—FILICJNEJE—OPIJJOCI.OSSACRAi 231 

aquatic organism like the gametophyte of all Muscineae. In the 
few cases where true roots are absent their phce is taken by 
other structures that perform their functions. The assimilative 
activity is restricted to special organs, the leaves, except in a few 
cases where these become much reduced, as in Psilotum or Eqiii- 
sctmn. A main axis is present upon which the leaves are borne 
as appendages, and this continues to form new leaves and 
roots as long as the sporophyte li^/es. 

The differentiation of these special organs begins while the 
sporophyte is still very young. The earliest divisions in the 
embryo correspond closely to those in the embryo of a liryo- 
phyte, but instead of forming simply a capsule, as in all the 
Bryophytes, there is established more than one growing point, 
each one forming a distinct organ. In the typical Ferns there 
are four of these primary growing points, giving rise respect- 
ively to the stem, leaf, root and foot. The latter is a tem- 
porary structure, by which the young sporophyte absorbs food 
from the gametophyte, but as soon as it becomes independent 
the foot gradually withers away, and soon all trace of it is lost. 

The originally homogeneous tissues of the embryo become 
differentiated into the extremely complicated and varied tissues 
characterising the mature sporophyte. The most characteris- 
tic of these is the vascular system of tissues. This is hinted at 
in the central strand of tissue in the seta of many Mosses, and 
the columella of the Anthocerotes ; but in no Bryophyte does 
it reach the perfect development found in the Ferns and their 
relations, which are often called on this account the Vascular 
Cryptogams. 

The gradual reduction in the vegetative parts of the game- 
tophyte, from the large long-lived prothallium of the Marat- 
tiacere to the excessively reduced one found in the heterosporous 
Pteridophytes, has already been referred to in the introductory 
chapter. 

The structure of the sexual organs of the Pteridophytes 
appears at first sight radically different from that of the 
Bryophytes, but a careful comparison of the lower forms of the 
former with some of the Hepaticse, and especially with the 
Anthocerotes, shows that the difference is not so great as it at 
first sight appears. A further discussion of this point must be 
left, however, until we have considered more in detail the struc- 
ture of these parts in the different groups of the Pteridophytes, 



212 MOSSES AND FERNS chap. 

where they are remarkably uniform. In all of them the arche- 
gonium has usually a neck composed of but four rows of per- 
ipheral cells, instead of five or six, as in the Bryophytes, and the 
antheridium, except in the leptosporangiate Ferns, is more or 
less completely sunk in the tissue of the prothallium. The 
spermatozoids are either biciliate, as in Mosses, or multiciliate, 
a condition which, so far as is known, does not exist among the 
Bryophytes. 

The formation of spores is very much more subordinated 
to the vegetative life of the sporophyte than is the case among 
the most highly organised of the Bryophytes. Indeed it may be 
many years before any signs of spore formation can be seen. 
The spores are always born in special organs, sporangia, which 
are for the most part outgrow^ths of the leaves, but may in a 
few cases develop from the stem. In the simplest cases the 
spores arise from a group of hypodermal cells, generally trace- 
able to a single primary cell. The cell outside of these divides 
to form a several-layered wall, but the limits of the sporangium 
are not definite, and it may scarcely project at all above the 
general surface of the leaf. From this "eusporangiate" condi- 
tion found in Ophioglossum, there is a complete series of forms 
leading to the so-called leptosporangiate type, where the whole 
sporangium is directly traceable to a single epidermal cell, and 
where a very regular series of divisions takes place before the 
archesporium is finally formed. 

With very few exceptions all of the existing Pteridophytes 
fall naturally into three series or classes of very unequal size. 
The first of these, the Ferns or Filicinese, is the predominant 
one at present, and includes at least nine-tenths of all living 
Pteridophytes. The Equisetinese are the most poorly repre- 
sented of the modern groups, and include but a single genus 
with about twenty-five species. The third class, the Lyco- 
podinese, is much richer both in genera and species than the 
Equisetinese, but much inferior in both to the Filicinese. The 
disproportion between these groups was much less marked in 
the earlier periods in the world's history, as is attested by the 
very numerous and perfect remains of Pteridophytes occurring 
especially in the coal-measures. At that time both the 
Equisetinese and Lycopodinese were much better developed 
both in regard to size and numbers than they are at 
present. 



VII PTERIDOPHYTA—FIUCINEAl—OPHIOGLOSSACEAi 2:sZ 

Class I. Filicine.^ (Filicales) 

The Filicinese or Filicales, as already stated, include by far 
the greater number of existing Pteridophytes, and are much 
more extended in range and abundant in numbers than either of 
the other classes. A marked characteristic of all Ferns is the 
large size of the leaves, which are also extremely complicated 
in form in many of them. In a few of these the leaves are 
simple, e. g., Ophioglossiim, Vittaria, I'ihilaria, but more com- 
monly they are pinnately compound and sometimes of enormous 
size. The stem varies a good deal in form and may be very 
short and completely subterranean, as in species of Ophioglos- 
siim and Botrychium, or it may be a creeping rhizome, or in 
some of the large tropical Ferns it is upright, and grows to a 
height of 8 to lo metres, or even more. 

While some forms of the Ferns are found adapted to almost 
all situations, most of them are moisture-loving plants, and 
reach their greatest development in the damp mountain forests 
of the tropics. A few, e. g., Ceratoptcris, AzoUa, are genuine 
aquatics, and still others, c. g., species of Gymnogrammc, live 
where they become absolutely dried up for several months each 
year. These latter will quickly revive, however, as soon as 
placed in water, and begin to grow at once. In the tropical 
and semi-tropical regions many Ferns are epiphytes, and form 
a most striking feature of the forest vegetation. With few ex- 
ceptions the sporophyte is long-lived, but a few species are 
annual, e. g., Ceratopteris, and depend mainly upon the spores 
for carrying the plant through from one season to another. 
The sporophyte may give rise to others by simply branching in 
the ordinary way, or special buds may be developed either from 
the stem or upon the leaves (Cystopteris hulhifera). 

Besides the normal production of the gametophyte from 
the spore, it may arise in various ways directly from the 
sporophyte (apospory) ; and conversely the latter may develop 
as a bud from the gametophyte without the intervention of the 
sexual organs (apogamy). 

The Filicinese include both eusporangiate and leptospo- 
rangiate forms, — indeed the latter occur only here. The former 
comprise the homosporous orders, Ophioglossales and Maratti- 
ales, and possibly the heterosporous order Isoetales, whose sys- 
tematic position, however, it must<be said is still doubtful. The 



234 MOSSES AND FERNS chap. 

Leptosporangiatae include the single great homosporous order 
Filices, and the two heterosporous families, closely related to 
it, the Salviniacese and the Marsiliacese. These are usually 
classed together as a distinct order, the Hydropterides or 
Rhizocarpese. 

The Filicine^ Eusporangiat^ 

The two orders, Ophioglossales and Marattiales, show 
many evidences of being very ancient forms, and in several 
respects seem to approach more nearly to the Hepaticse than any 
other Pteridophytes. While they are different from each other 
in many respects, still there is sufficient evidence to indicate 
that they belong to a common stock to warrant placing them 
near each other in the system. 

The Ophioglossales 

The three genera belonging to this order may all be united 
in a single family, Ophioglossacese. 

The Ganietophyte 

Our knowledge of the gametophyte of the Ophioglossacese 
has been very much augmented during the past ten years. Jef- 
frey (i) has described very fully the gametophyte of Botry- 
chiiim Virginiamim, and Lang (4) and Bruchmann (5) have 
made out the most important facts in that of Ophioglossum and 
Helminthostachys. Our earlier knowledge was based entirely 
upon the fragmentary observations of Hofmeister (i) upon 
Botrychmm lunaria, and those of Mettenius (2) upon Ophio- 
glossum pediinciilosum. 

The writer has succeeded in securing the earliest phases of 
germination in two species, viz., Ophioglossum (Ophio- 
dernia) pendulum and Botrychium Virginianum, as well as the 
older prothallia of the latter. The germination in both cases 
is extremely slow, especially in the former, where a year and a 
half after the spores were sown the largest prothallia had but 
three cells. Probably under natural conditions the growth is 
more rapid. The spores of both forms show much the same 
structure. The tetrahedral spores contain granular matter, 



VII PTERIDOPHYTA—FILICINEAl—OPHIOGLOSSACEJE 235 




with numerous oil-drops, and a central lar,e^e and distinct 
nucleus. The exospore is colcjurless, and upon the outside 
presents a pitted appearance in Ophioglossuni, and irrej:^u]ar 
small tuhercles in Botrycliiiini. The jicrinium or epis])ore is not 
clearly distinguishable from the exospore. in both cases 
chlorophyll is absent in the ripe spore. The first sign of ger- 
mination is the absorption of water and splitting of the exospore 
along the three radiating lines en the ventral surface of the 
spore. The spore enlarges considerably before any divisions 
occur, but remains globular in form, and no 
chlorophyll can be detected. In this con- 
dition, which was observed within two 
weeks after the spores were sown in Ophio- 
glossnm, it may remain for several months 
unchanged. The first division wall is 
usually at right angles to the axis of the 
spore, and divides it into two nearly equal 
cells, of which the lower has more of the 
granular contents than the upper one. The 
endospore is noticeably thickened where it 
protrudes through the ruptured exospore. 
The next wall, in all cases observed, is at 
right angles to the first, and always in the 
lower cell, which it divides into equal parts 
(Figs. 124, 125). In Botrychmm at this 
stage a few large chloroplasts were seen in 
both upper and lower cells, but Ophioglos- 
sum showed no positive evidence of 
chlorophyll, although it seemed sometimes 
as if a faint trace of chlorophyll could be 
detected. As growth proceeds, the oil 
partially disappears, and the cells become 
much more transparent than at first. 

Lang (4) found the prothallia of Ophioglossum pendulum 
burled in the humus collected about masses of epiphx-tic ferns 
among which the sporophytes of the Ophioglossum were grow- 
ing. The youngest ones discovered were nearly circular in out- 
line, the older specimens more or less branched (Fig. 125, C). 
The branches are cylindrical and grow from a single initial cell 
which has the form of a four-sided pyramid. The lower half 
of the prothallium is infested by an endophytic fungus, while 




Fig. 124. — Germinating 
spore of Ophioglossum 

{Ophio derma) pendu- 
lum. A, Surface view; 

B. optical section, 

X600. 



236 



MOSSES AND FERNS 



CHAP. 



from the upper side of the thallus the reproductive organs are 
developed. Numerous rhizoids grow from the superficial cells. 
Mettenius (2) has described the gametophyte in O. pedun- 
culosum, which agrees in the main with that of O. pendulum. 
In this species, however, there is first developed a ''primary 
tubercle" (Fig. 125, B), and the branches were observed in 
some cases to grow above the ground, where they became flat- 
tened and developed chlorophyll. 




Fig. 125. — A, B, Prothallia of Ophioglossum pedunculosum, Xi/4; B, shows the 
young sporophyte, with the cotyledon and first root, r; t, the primary tubercle. 
C-F, O. pendulum. C, An old prothallium, X6; D, nearly ripe antheridium; E, 
surface view of antheridium, showing the opercular cell; F, nearly ripe arche- 
gonium; D-F, X about 275; (A, D, after Mettenius; C-F, after Lang). 



The Sex-Organs 

The antheridium arises from a superficial cell which divides 
by a periclinal wall into an inner cell, from which by further 
divisions the mass of sperm-cells is derived, and an outer one, 



VII PTERIDOPHYTA—FILICINEAL—OPHIOGLOSSACE/E 237 

from which the cover of the anthcri(huni is formed. The outer 
wall of the antheridium remains for tlie most part but one cell 
thick, in this respect more resembhng- Marattia than it does 
Botrychmm. The antlieridium also opens by a single, nearly 
triangular opercular cell (Fig. 125, E), as it does in Marattia. 
The spermatozoids were not seen, but probably resemble those 
of Botrychiiim or Marattia. 

The first division of the young archcgonium is the same as in 




^ ..$ 




D 





Fig. 126. — A, Longitudinal section of a large prothallium of Botrychium J'irginianum, 
X15; B, transverse section of a somewhat younger one, showing the antheridial 
ridge, and the archegonia; C, prothallium of Hclminthostachys Zcylanica, X7; 
D, young antheridium of Helminthostachys, X22S. (C, D, after Lang.) 



the antheridium. From the inner cell, after it divides into a 
basal and a central cell, is formed the axial row of cells — the 
egg cell and the canal cells. No division of the neck canal cell 
was observed beyond the division of the nucleus, and the ventral 
canal was not seen ; but the latter is doubtless formed before the 
archegonium is mature. 

The neck of the archegonium remains very short, scarcely 



238 MOSSES AND FERNS chap. 

projecting at all above the surface of the prothallium, and 
closely resembling in form the archegonium of the Marattiacese. 
Each of the four rows of neck cells contains three or four cells. 
The basal cell may undergo divisions, but its limits remain 
clearly visible in the ripe archegonium. 

According to Mettenius ((2) PI. xxx, Figs. 18, 19), O. 
pedunciilosiim differs from 0. pendulum in having the outer 
wall of the antheridium double, as it is in Botrychium. The 
neck of the archegonium is also somewhat longer than in 
O. pendulum. Bruchmann's account of 0. vulgatum agrees 
closely with that of Lang for 0. pendulum. 

Botrychium 

In July, 1903, the writer found at Grosse Isle, Michigan, a 
number of old prothallia of Botrychium Virginianum, with the 
young sporophytes still attached, but nevertheless showing the 
older stages of the sexual organs. In 1896, Jeffrey (i) was 
fortunate enough to secure abundant material of this species, 
including young prothallia, and succeeded in tracing very com- 
pletely the development of the reproductive organs and embryo. 
Owing to the kindness of Professor Jeffrey, who sent preserved 
material, as well as prepared slides, I have been able to confirm 
the results of his investigations. 

The prothallium (Figs. 126, 127) is a subterranean, tuber- 
ous body, much like that of B. lunaria described by Hofmeister, 
but is very much larger. The specimens collected by the writer 
were buried several centimetres below the surface, in rather dry 
woods ; Jeffrey's material was in part found in a sphagnum bog, 
partly in dryer localities. 

The youngest specimens found by Jeffrey were oval, slightly 
flattened bodies, which bore only antheridia. These occupied 
the middle line of the upper surface, which later develops a 
median ridge upon which the antheridia are borne, while arche- 
gonia appear later on either side of the antheridial ridge. (Fig. 
126, B). In B. lunaria, according to Hofmeister ((i), p. 
308), the archegonia are mostly formed upon the ventral 
surface. 

A section of the prothallium shows that the superficial tis- 
sues are composed of relatively transparent cells, while the inner 
tissue, especially toward the ventral side of the thallus, has very 
dense contents, there being an oily substance present, as well as 



vu PTERIDOPHYTA—FILICINE^—OPHIOGLOSSACEJE 239 



granular matter. In these cells is found an enckjphytic fungus, 
which probably acts as a mycorhiza. Multicellular hairs are 
found growing from the upper surface of the prothallium. 

The growth of the prothallium is distinctly apical, and a 
single definite apical cell seemed to be present, although it is 
possible that there may be more than one initial. 

The infection of the thallus by the mycorhizal fungus is 
chiefly through the short rhizoids upon the inferior surface of 
the thallus. Jeffrey concludes that the affinities of the fungus 
are with the genera Pythium or Coinplctorio. 






^ -^ 



Fig. 127. — Botrychiitm Virgiyiianum. A, B, Germinating spore, X6oo; C, pro- 
thallium {pr), with young sporophyte attached, X2; D, longitudinal section of the 
prothallium, showing the foot of the embryo (F), X4; E, first (?) leaf of a 
young sporophyte, X2. 

As the prothallium grows older — it may evidently live for 
several years — it becomes irregular in outline. It may finally 
reach a length of twenty millimetres, and occasionally shows in- 
dications of a dichotomy of the apex. 

Sex-Organs 
The first antheridia form a small group upon the upper sur- 
face of the prothallium while it is still very young. The later 
ones form only upon the median ridge already referred to. 



240 



MOSSES AND FERNS 



CHAP. 



Still later the archegonia appear along the base of the anther- 
idial ridge (Fig. 126, B). 

The development of the antheridium (Fig. 128) is much 
like that of Ophioglossum, but the outer wall of the antheridium 
has normally two layers of cells. The spermatozoids, accord- 
ing to Jeffrey, probably correspond with those of the true Ferns. 
In a few cases observed by myself (Fig. 128, C) the primary 
division walls of the central part of the antheridium were not 
broken down by the separation of the sperm cells, but formed a 
number of chambers. 

The complete spermatozoid has about one and a half coils. 



B. 



A. 




Fig. 128. — Boirychium Virginianum. Development of the antheridium, X about 450; 
in C, the primary division walls within the antheridium have persisted, forming 
large chambers, from which the ripe sperm-cells are ejected successively. 



and closely resembles that of the true Ferns and Equisetum, 
like them having numerous cilia. They swarm within the 
antheridium, and according to Jeffrey's account, escape through 
on opening formed by the destruction of two superimposed 
cells of the outer wall. They do not all escape at once, but are 
ejected in separate swarms. It is possible that the formation 
of the separate chambers, noted by the writer, may have some- 
thing to do with this phenomenon. 

The development of the archegonium (Fig. 129) is much 
like that of Ophioglossum, but the neck of the archegonium is 
much longer and projects conspicuously above the surface of 



VII PTERIDOPHYTA-PILICINE^—OPIIIOGLOSSACEJE 24I 

the thallus. The basal cell also divides more extensively, but 
the group of cells derived from it is easily recognisable in the 
ripe archegonium. 

The central cell divides transversely, the lower cell forming 
the Qgg, and the ventral canal cell, the up])er one giving rise 
to the single neck canal cell, whose nucleus later divides as in 
Ophioglossum. 

The mature ^gg cell contains dense cytoplasm, but has a 
vacuole within it. Jeffrey observed a spermatozoid in the act 
of penetrating the ^gg, which showed an extension toward the 
entering spermatozoid. The details of fertilisation, however, 




Fig. 129. — Botrychium Virginianum. Development of the archegonium, X about 450. 

were not made out, but they probably correspond closely with 
those observed in other Ferns. 



Helminthostachys 

The gametophyte of Helminthostachys (Lang (4)). the 
third genus of the Ophioglossacese, does not differ essentially 
from the other genera, being also subterranean. It is nearly 
cylindrical in form (Fig. 126, C). The lower part, which is 
brown, and covered with rhizoids, is sterile, and contains an 
16 



242 



MOSSES AND FERNS 



CHAP. 



endophytic fungus. The upper portion, hghter in colour, bears 
the reproductive organs. Some of the prothalha bear only 
antheridia; the others have archegonia as well. As usual, the 
first antheridia appear before any archegonia are formed. Both 
archegonia and antheridia resemble those of Botrychium more 
than they do those of Ophioglossiim. 

The Embryo 

The fertilised tgg, or oospore, becomes invested with a cell- 
membrane and enlarges to several times its original bulk before 




Fig. 130. — Botrychium Virginianum. A, two-celled embryo within the archegonium 
venter, X about 300; B, two sections of an 8-celled embryo; C, large embryo 
showing the primary organs, X about 25. 



the first division wall is formed. This primary (basal) wall is 
in most cases transverse, but may be somewhat oblique. The 
two cells are generally more or less unequal in size, the upper or 
epibasal cell being larger than the lower (hypobasal) one. 
Each primary cell is next divided by a median vertical wall, and 
the young embryo shows thus a regular quadrant formation. 
The next divisions occur in the epibasal quadrants and are also 
approximately transverse ; at this stage, to judge from Jeffrey's 
figures 43, 44, the embryo presents a striking resemblance to a 
corresponding stage in Anthoceros. 



VII PTERIDOPHYTA—FILICINEAi—OPlIIOGLOSSACEAi 243 

The subsequent divisions apparently show great irregu- 
larity, and the embryo does not exhil)it the early development 
of apical initial cells so marked in the typical h>rns. 

The whole epibasal part of the embryo is devoted to the for- 
mation of the foot, in this respect showing an analogy, at least 
with Anthoccros. From the epibasal region arise the shoot and 
the root, both of which later develop a definite ai)ical cell. The 
initial cell of the root at once begins to form ])ericlinal cells, 
which cut ofif the segments of the root caj) from its fjuter face, 
and the apical cell thus becomes deeply sunk beneath the surface 
of the root-apex, which projects but little beyond the other parts 
of the very massive embryo-sporophyte. The primary leaf, or 
cotyledon (Fig. 130 cot.), unlike that of the true Ferns, arises 
secondarily from the shoot. 

In one instance, Jeffrey found small tracheids present in a 
prothallium, but the young sporophyte had been destroyed, and 
there w^as no means of determining whether this formation of 
tracheids was associated with apogamy, as in all other similar 
cases that have been observed. 

The tissues adjacent to the venter of the archegonium grow 
rapidly, keeping pace with the developing embryo, which 
becomes very large before it breaks through the overlying 
tissues (calyptra), which protect it. At this time, the very 
large foot is especially conspicuous. The root is already some- 
what elongated and show^s a very definite arrangement of its 
tissues, which resembles that of the later roots. A tetrahedral 
apical cell is covered by a root-cap composed of several layers 
of cells, and the axis of the root is occupied by a strand of nar- 
row cells, which later develop into the vascular cylinder or 
''stele" of the root. 

The cotyledon, at this time, is relatively inconspicuous, and 
forms a short, incurved, conical protuberance, between which 
and the root lies the very slightly conical apex of the shoot. 
Both stem and leaf show a fairly distinct apical cell, but these 
apparently cannot be traced back to the original embryo-octants, 
as is the case in the more specialised Ferns. A very short 
procambium cylinder can somewhat later be seen in the axis 
of the stem, and from it extends a similar strand into the cotyle- 
don. The central cylinder of the stem (Jeffrey (i), p. 21) 
becomes fully developed below the point of origin of the 
cotyledon. From the first it is a hollow cylinder with a well- 



244 MOSSES AND FERNS chap. 

marked pith. The vascular ring is broken by a gap above the 
first leaf-trace ( cotyledonary stele), and the pith is thus thrown 
into communication with the outer ground tissue, or cortex. 

The first tracheary tissue appears shortly after the root has 
broken through the calyptra, at which time the root has the 
length of 5-20 millimetres. The development of the tracheary 
tissue in the root begins at two, or more commonly three, 
points, i. e., the root is either "diarch" or "triarch." The in- 
nermost layer of the fundamental tissue forms the "endoder- 
mis" or bundle-sheath. As is usually the case, the endodermal 
cells are characterised by the peculiar thickening or foldings of 
the radial walls, which appear as elongated dots in transverse 
sections. A similar endodermis can be made out, surrounding 
the stelar tube of the stem. 

The primary tracheids, or "protoxylem," have reticulately 
sculptured walls, and, except in size, closely resemble the secon- 
dary tracheary elements, or "metaxylem," which are formed 
centripetally, and meet in the centre of the vascular cylinder. 
Between the xylem masses are as many masses of phloem, or 
bast, made up in part of sieve-tubes with which are mingled 
elongated paranchyma cells. Surrounding the circle of xylem 
and phloem masses is the pericycle, composed of one or two 
layers of parenchyma. 

After the young root has broken through the calyptra and 
penetrated the ground, the cotyledon grows upward and finally 
makes its appearance above the surface of the ground. It 
becomes differentiated into a slender, nearly cylindrical stalk 
(stipe) and a much-divided lamina (Fig. 127, E). The single 
primary vascular bundle of the leaf-rudiment divides into two 
within the stalk, and passes into the two lateral lobes of the 
lamina. From one of them a strong branch is developed which 
constitutes the midrib of the central segment of the lamina. 
The vascular bundles of the stipe approach the collateral type, 
rather than the concentric structure found in the later formed 
leaves. 

Sometimes two or three roots are developed before the 
cotyledon unfolds, and the young sporophyte remains for a long 
time — probably two or three years — attached to the gameto- 
phyte, the superficial cells of the foot remaining active during 
this period. These cells show the dense cytoplasm and con- 
spicuous nuclei of active cells. . -- 



VII PTERIDOPHYTA—FILICINE^—OPHIOGLOSSACEJE 245 

According to Mettenius, the cotyledon in OpJiioglossum 
pednncnlosmn develops much earlier than is the case in 
Botrychhim. It appears above the ground while the primary 
root is still but little developed. (Fig. 125, B.) 

In Botrychium lunaria, according to Hofmeister, the first 
three leaves are rudimentary and the first green leaf does not 
appear above ground until the second year. 

Mettenius' account of the development of the embryo in 
O. pedunculosum is less complete. The earliest stage seen by 
him was already multicellular, and the young embryo had the 
form of an oval cell mass in which the primary divisions were 
not recognisable. The upper part, i. e., that next the arche- 
gonium. neck, grows up at ^once into the cotyledon, while the 
opposite part gives rise to the first root. These grow respect- 
ively upw^ard and downward*, and break through the overlying 
prothallial cells. Later, at a point between the two, the stem 
apex is developed. The first leaf becomes green, and develops 
a lamina similar to that of the later-formed ones. Usually but 
one embryo is developed from the prothallium, but occasionally 
two are formed, especially where the prothallium forks. 

The Adult Sporophyfe 

Ophioglossiim (Ophioderma) pendulum, an epiphyte com- 
mon in the Eastern tropics, may be taken as a type of the sim- 
plest of the Ophioglossacese. Its short creeping stem grows 
upon the trunks of trees, especially tree-ferns, from which the 
long flaccid leaves hang down. The lamina of the leaf merges 
insensibly into the stout petiole whose fleshy base forms a sheath 
about the next younger leaf. Corresponding to each leaf is a 
thick unbranched root, which penetrates into the crevices of 
the bark and holds the plant secure. These roots are smooth, 
and show no trace of rhizoids. The petiole is continued up into 
the lamina as a very broad and thick midrib, which in the spo- 
riferous leaves (sporophylls) is continued into the peculiar 
elongated spike which bears the sporangia. 

The petiole if cut across shows a number of vascular bundles 
arranged in a single row, nearly concentric with the periphery 
of the section. As these enter the lamina they anastomose and 
form a network with elongated meshes (Fig. 133, C) and no 
free ends. Sections of the spike cut parallel to its broad 




Fig. 13:. — Ophioglossiim pendulum. A, Leaf with sporangiophore, natrual size; B, 
cross-section of the petiole, X6; C, section of the sporangiophore, parallel to tts 
broad surface, X6. 



VII PTERIDOPHYTA—FILICINEJE—OPHIOGLOSSACE^ 24.7 



diameter show a somewhat similar arran<^rement of the vascular 
bundles, but here there are free brandies exteiKhng between the 
sporangia. The relations of the bundles of the fertile and sterile 
parts of the leaf are best 
followed in the smaller 
species. Prantl ((7), p. 
155) describes it as fol- 
lows for O. Liisitanicum, 
and states that it is essen- 
tially the same in other 
species. ''The primary 
bundle given off from the 
stem branches just after it 
enters the petiole. The 
main bundle gives off two 
smaller lateral branches 
right and left. The latter 
branch again near the base 
of the sporangiophore,and 
the upper branches from 
each unite to form the sin- 
gle bundle that enters the 
latter." 

The sporangia are 
sunk in the tissue of the 
sporophyll, and scarcely 
project at all above the 
surface, where the position 
of each one is indicated 
by a faint transverse fur- 
row which marks the 
place where it opens. 
Seen in sections parallel to 
the flat surface these ap- 
pear perfectly round, but .^ 
in transverse section are^ 
kidney-shaped (Fig. 
140, C). 

The apex of the stem forms a blunt cone, which, however, is 
not visible from the outside. A longitudinal section through 
the end of the stem shows that it is covered by a sheath com- 




FiG. 1^2.^0 phioglossum vulgaUim, X i. 



24« 



MOSSES AND FERNS 



CHAP. 



posed of several layers of cells, and this encloses a cavity in 
which are the growing point of the stem and the youngest leaf. 
The leaves here form much more rapidly than in the species of 
the temperate regions, as the growth continues uninterruptedly 
throughout the year. The real apex of the stem forms an in- 
clined nearly plane surface, slightly raised in the centre, where 
the single apical cell is placed (Fig. i34,A,B). This cell is by no 
means conspicuous, and not always readily found, but probably 

is always present. It has 
the form of an inverted 
three-sided pyramid, but the 
lateral faces are more or less 
strongly convex, and the 
apex may be truncate. From 
the few cases observed it is 
not possible to say whether 
in addition to the three sets 
of lateral segments basal seg- 
ments are also formed, but it 
is by no means impossible 
that such is the case. Ac- 
cording to investigations of 
Rostowzew ((i), p. 451), 
the apical cell of the stem 
of Ophioglossiim vulgatum 
shows considerable variation, 
and may be either a three or 
four-sided prism, i. e., it ap- 
^ , . , , , . ,, parently also may have the 

riG. 133. — Ophioglossuni pendulum. A, Me- | -^ > / \ 

dian longitudinal section of stem apex, X4; uaSC trUnCatC. JriOlle S \^ ) 
^, the growing point; B, young sporophyll, ^gg^j.-^jQj^ ag-rCCS with this 
X2; sp, the sporangiophore; C, an older '- ^ 

leaf, showing the venation, X2. CXCCpt that he StatCS that he 

always found the cell pointed 
below, not truncate. The segments cut off from the lateral 
faces are large, and the divisions irregular. They are appar- 
ently formed in very slow succession, and the irregularity of the 
succeeding divisions in the segments themselves soon makes it 
impossible to trace their limits. Each segment apparently gives 
rise to a leaf, but this is impossible to determine with certainty. 
The first wall in the young segment probably divides it into an 
inner and outer cell, but the next divisions could not be deter- 




VII PTERIDOPHYTA—FILICINEJE—OPHIOGLOSSACEJE 249 

mined positively. Probably, as in Botrychium, the outer cell is 
next divided by a vertical wall, ])erpendicular to the broad 
faces of the segment, into two cells, in which divisions then 
take place in both transverse and longitudinal direction without 
strict regularity. 

The stem in O. pendulum is mostly made up of thin-wallcd 
parenchyma, and the vascular bundles are much less developed 
than is the case in the underground stem of O. vulgatiim or 
Botrychium. The bundles are of the collateral form, /. c, the 
inner side is occupied by the xylem, the outer by the phloem, 




Fig. 134.^-Ophioglossum pendulum. A, Longitudinal section of stem apex, X6o; B, 
the central part of the same section, Xi8o; D, longitudinal section of very young 
sporangiophore, Xi8o; E, cross-section of young sporangiophore, X6o. 



and there is no evident bundle-sheath developed. The bundles 
form a very irregular wide-meshed cylinder, not differing essen- 
tially from that in O. vulgattui 

Van Tieghem (7) states that in Ophioglossum vuJgatum 
each vascular strand is completely invested with a distinct 
endodermis and pericycle; but Bower (16) found the endoder- 
mis very poorly developed in the species studied by him, 
especially 0. Bergianum, a small and simple species. The stem 
of this form shows in transverse section two strands which may 



250  MOSSES AND FERNS chap. 

either be separate, or partly coherent, so as to form a single 
crescent-shaped bundle, when seen in section. There may be, 
however, even in this species, more than two strands present. 
Poirault (2) found a definite endodermis in the lower part of 
the stem, which disappears in the upper portion. 

Van Tieghem asserts (see Bower (16), p. 67) that in the 
young sporophyte of O. vulgatum, there is at first a solid axial 
stele, with pericycle and endodermis, and that only above the 
insertion of the first leaf does a pith appear. 

In the bundles of the stem of 0. pendulum, the xylem of the 
collateral bundle is mainly composed of short irregular 
tracheids, with close reticulate markings on the walls. The 
phloem is composed of short, thin-walled cells with large nuclei. 
No true sieve-tubes could be recognised. 

The Leaf 

The young leaf is completely concealed by the sheath formed 
at the base of the next older one. It is at first a conical pro- 
tuberance arising close to the stem apex, around which its base 
gradually grows and forms the sheath about it and the next 
leaf rudiment. It is probable that here, as in 0. vulgatum,^ 
the young leaf grows at first by a definite apical cell. After 
the plant has reached a certain age, each leaf gives rise to 3. 
sporangial spike, which becomes evident while the leaf is still 
very small. The first indication of this is a conical outgrowth 
upon the inner surface of the leaf, about halfway between the 
apex and base. A longitudinal section of this shows it to be 
made up of large cells, especially toward the top ; but although 
there was sometimes an appearance that indicated the presence 
of a single apical cell, this was by no means certain, and if there 
is such an initial cell, its divisions must be very irregular. 

Bower (16) found that in O. vulgatum the young spo- 
rangial spike grows from a single apical cell, which in less robust 
specimens persists for a long time as a four-sided, initial cell, 
but in the larger specimens seems to be replaced by four similar 
initials. 

The subsequent growth of the leaf is for a long time mainly 
from the base, and the young sporangial spike is much nearer 
the apex in the next stage (Fig. 133, B). No distinct petiole 

^ Rostowzew (i); p. 451. 



VII PTERIDOPHYTA—FILICINEJE—OPHIOGLOSSACEJE 251 



has yet developed, but the centre of the young leaf, up to the 
point of attachment of the spike, is traversed by the thick mid- 
rib, above which the lamina is still very small. Indeed in this 
stage it looks as if the spike were really terminal and the lamina 
a lateral appendage. The young spike now forms a beak- 
shaped body curving inward and upward, and sections of 
slightly older stages than the one figured show the first indica- 
tions of the developing sporangia. Later still the base of the 
leaf becomes narrowed into the petiole, and the spike also 
becomes divided into the upper sporiferous portion and the 
short slender pedicel. 

The anatomical structure of the leaf is extremely simple. 
The epidermis is composed of 
rather thick-walled cells, irreg- 
ularly polygonal in outline, 
with large stomata at intervals, 
about which the cells are ar- 
ranged concentrically, and fre- 
quently with a good deal of 
regularity. The stomata them- 
selves (Fig. 135), seen from 
above, have an angular outline, 
but from below are perfectly 
oval, and cross-sections show 
that this appearance is due to a 
partial overarching of the 
guard cells of the stoma by the 
surrounding epidermal cells. 
The upper walls of the guard 
cells are thickened unequally, 

giving them the appearance of being folded longitudinally. 
There is no distinct hypoderma formed, and the bulk of the leaf 
is made up of a uniform mesophyll composed of nearly globular 
cells with much chlorophyll, and separated by numerous inter- 
cellular spaces. In the petiole the tissues are similar, but more 
compact, and the walls of the ground tissue are all deeply pitted. 
The vascular bundles are nearly circular in section and show 
a compact mass of tracheary tissue (Fig. 136, t), surrounded 
by nearly uniform cells with moderately thick colourless walls. 
The limits of the bundle are not, as in the higher Ferns, marked 
by a distinct bundle-sheath, but are indicated simply by the 




Fig. 135. — Stoma from the leaf of Ophio- 
glossum pendulum, X260. 



^5^ 



MOSSES AND FERNS 



CHAP. 



somewhat smaller size of the cells of the bundle itself — indeed 
it is not always easy to say exactly where the ground tissue 
begins. The xylem is composed of pointed tracheids whose 
walls are marked with thick reticulate bands. This mass of 
tracheary tissue is situated near the inner side of the bundle, 
which like that of the stem is collateral. The rest of the 
bundle is composed of sieve-tubes mingled irregularly with 
smaller cambiform cells. Whether or not sieve-tubes occur 
upon the inner side of the bundle could not be positively deter- 
mined. The sieve-tubes have transverse walls, and in 0. vul- 




FiG. 136. — Vascular bundle of the petiole of O. pendulum, X260; t, t, the xylem 

of the bundle. 



gatiim lateral sieve-plates have been observed. The spo- 
rangiophore has much the same anatomical structure as the rest 
of the leaf, but stomata are quite absent from its epidermis. 
In this respect O. pendulum differs from O. vulgatum and 
allied species, where stomata are developed upon the spo- 
rangiophore as well as upon the rest of the leaf. 

The Root 

The roots are formed singly near the bases of the leaves, 
and are light yellowish brown in colour, and so far as could be 



VII PTERIDOPHYTA—FILICINEJE—OPHIOGLOSSACEJE 253 

seen, entirely unbranched. Sections show that here, as in most 
vascular plants, the growing point of the root is not at the apex, 
but some distance below and protected by the root-cap. The 
growth of the root in Ophioglossuin can be traced to a single 
apical cell (Fig. 137), which is of large size, and, like that of 
the stem, approximately pyramidal in form. While the divi- 
sions show greater regularity than in the stem, still they are 
very much less so than in the leptosporangiate Ferns. Seg- 
ments are cut off not only from the lateral faces of the apical 
cell, but also from its outer face. These outer segments help 
to form the root-cap, which, however, is not derived exclusively 





Fig. i27.^0phioglossum pendulum. A, Longitudinal; B, transverse sections of 

the root apex, X215. 



from these, but In part also from the outer cells of the lateral 
segments. Each of the latter is first divided by a nearly ver- 
tical wall, perpendicular to its broad faces, into two "sextant 
cells," but beyond this no regularity could be discovered in the 
order of division in the segments, and the tissue at the growing- 
point, especially in longitudinal section, presents a very con- 
fused arrangement of the cells. A little lower down two 
regions are discernible, a central cylinder (plerome), whose 
limits are not very clearly defined, and the periblem or cortex. 
A definite epidermis is not distinguishable. 

The first permanent tissue in the plerome cylinder or stele, 
which is elliptical in section, arises in the form of small tracheids 



254 



MOSSES AND FERNS 



CHAP. 



near the foci of the elhptical section. From here the formation 
proceeds towards the centre, and in the full-grown root the 
tracheary tissue forms a continuous band occupying the larger 
axis of the section, the last-formed tracheids being the largest. 
On either side of this tracheary plate is a poorly defined mass 
of phloem, similar to that of the stem and leaf bundles. An en- 
dodermis or bundle sheath can be made out, although it is much 
less prominent than in most roots. The endodermis is derived 
from the innermost cortical layer, and the radial cell-walls are 
characterised by a thickening, or folding of the wall. In O. vul- 

gatum the bundle of 
the root is diarch to 
begin with, but by the 
suppression of one of 
the phloem masses it 
becomes monarch. 

The Sporangium 

The development 
of the sporangium has 
been studied by 
Goebel ((17), p. 
390), in O. vulgatum, 
and recently by Bower 
(16) in this species 
and in 0. pendulum. 
The latter has been 
carefully examined by 
the writer, and the re- 

FiG. z3S.-0.pendulum.^ Vascular bundle of the root, g^j^g confirm that of 
Xos. The phloem is shaded; en^ endodermis. 

the latter investigator, 
except that it seems possible that the archesporium may be 
traced to a single cell, as Goebel asserts is probably the case in 
O.vul gatum. 

According to Bower (16), in all species examined by him, 
the sporangia arise from a continuous band of superficial tissue, 
on each side of the spike. To this he gives the name, "sporan- 
giogenic band." The sporangia arise from the sporangiogenic 
band, at more or less definite intervals, separated by intervals 
of sterile cells. In the sporangial areas, periclinal walls sep- 




VII 



PTERIDOPHYTA—FILICINE^—OPHIOGLOSSACEJE 255 



arate an inner archesporium from the outer cells, destined to 
form the wall of the sporangium. Between the young spo- 
rangia the cells form sterile septa. The cell-groups which form 
archesporia, and those which develop into sterile septa, are 
sister-cell groups. 

All of the sporogenous tissue cannot be traced back to the 
primary archesporial cell, as later secondary sporogenous tissue 
may be formed by further periclinal divisions in the outer cells 
of the sporangium. 

A transverse section of the very young sporangiophore is 



A. 



B. 




Fig. 139. — A, Very young; B, older sporangia of O. pendulum; transverse sections, 

X260. 



somewhat triangular, the broader side corresponding to the 
outer surface of the sporangiophore. The cells are very irreg- 
ular in form, and no differentiation of the tissues is to be 
observed. Sections of somewhat older stages show in some 
cases, at least, a large epidermal cell occupying nearly the 
centre of the shorter sides of the triangular section. This cell 
has a larger nucleus than its neighbours, and is decidedly 
broader. The next stage was not observed, but a somewhat 
more advanced one shows a small group of inner cells (shaded 
in the figure), which appear to have arisen from the primary 



256 



MOSSES AND FERNS 



CHAP. 



cell by a transverse wall, although this point is exceedingly 
difficult to determine on account of the great similarity of all 
the cells (Fig. 139). This group of inner cells (or the single 
one from which they perhaps come) constitutes the arche- 
sporium, and by rapid division in all directions forms a large 
mass of cells whose contents become denser than those of the 




Fig. 140. — Ophioglossum pendulum. A, Section of a young sporangium, the arch- 
esporial tissue is shaded, the inner cells with dark nuclei being the definitive 
sporogenous cells, X200; B, transverse section of an older sporangium; sp, 
sporangeous cells; t, tapetum, X about 35; C, a portion of B more highly magni- 
fied; D, section of nearly mature sporangial spike, X8. 



surrounding ones, between which and these, however, the limits 
are not very plain. Later, when the number of cells is com- 
plete, the difference between them and the sterile tissue of the 
sporangiophore is much more evident. 

The cells lying outside of the archesporium divide rapidly 
both by longitudinal and transverse walls, and form the thick 
outer wall of the sporangium. In longitudinal sections, two 



VII PTERIDOPHYTA—FILICINE^—OPHIOGLOSSACE^ 2S7 

rows of cells may be seen extending from the mass of arche- 
sporial cells to the periphery. In these rows the vertical walls 
have been more numerous than in the adjacent ones, so that 
the number of cells in these rows is greater. It is between 
these rows of cells that the cleft is formed by which the ripe 
sporangium opens. The outer cells of the sporogenous tissue 
do not develop into spores, but constitute the "tapetum" (Fig. 
140, B, t), which serves to nourish ihe developing spores. 

After the full number of cells is reached in the archesporium, 
their walls become partially disorganized, and the cells round 
off and separate, exactly as in the sporogonium of a Bryophyte, 
and each cell is, potentially at least, a spore mother cell. 
Bower (16) states that only a part of the cells produce spores, 
and that the rest remain sterile and serve with the disorganised 
tapetal cells to nourish the growing spores. The final division 
of the spore mother cells into four spores is identical with that 
of the Bryophytes. 

At maturity the sporangium opens by a cleft, whose position 
is indicated as we have seen in the younger stages, and as the 
cells shrink with the drying of the ripe sporangiophore the 
spores are forced out through this cleft. 

Ophioglossum vulgatum and the other terrestrial forms 
show some points of difference when compared with 0. pen- 
dulum. These grow much more slowly, and longitudinal sec- 
tions of the upper part of the subterranean stem show several 
leaves in different stages of development. Each leaf rudiment, 
as in O. pendulum, is covered by a conical sheath, formed at 
the base of the next older leaf, and these sheaths are open at the 
top, so that there is direct communication between the outside 
air and the youngest of these sheaths which encloses, as in the 
latter species, the youngest leaf rudiment and stem apex (Ros- 
towzew ( I ) , p. 45 1 ) . In these terrestrial forms, also, the 
sporangiophore is longer stalked, and the lamina of the leaf 
more clearly separated from the petiole, which is not continued 
into it. The lamina is relatively broader and the venation more 
complex, in some species showing also free endings to the ulti- 
mate branches. The sporangia, too, project more strongly 
and are very evident (Fig. 132). Branching of the roots 
occurs occasionally, and according to Rostowzew may be either 
spurious or genuine. In the first place an adventive bud, which 

ordinarily would develop into a stem, develops a single root and 
1.7 



258 MOSSES AND FERNS chap. 

then ceases to grow. This root appears to be formed directly 
from the main root, and as the latter continues to grow the effect 
is that of a true dichotomy. The latter does occur, but not 
frequently. 

The formation of adventitious buds upon the roots is the 
principal method of propagation of some species of Ophioglos- 
siim, whose prothallia, as we have seen, are apparently very 
seldom developed. Rostowzew states that these are not de- 
veloped from the apical cell of the root, but arise from one of 
the younger segments, and the apical cell of the bud is produced 
from one of the outer cells of the young segment, but is covered 
by the root-cap, through which the bud afterwards breaks. 
The sheath covering the first leaf of the bud is formed from the 
cortex of the root and the root-cap. 

Differing most widely from the other species in general 
appearance is the curious epiphytic 0. (Cheiroglossa) palma- 
tiim. In this species the leaf is dichotomously branched, and 
instead of a single sporangiophore there are a number arranged 
in two rows along the sides of the upper part of the petiole and 
the base of the lamina. 

According to Bitter ( ( i ) p. 468) , 0. pendulum also has the 
sterile leaf segment dichotomously divided, but this was never 
the case in the specimens collected by the writer in various parts 
of the Hawaiian Islands. These invariably had an undivided, 
strap-shaped leaf. 

In O. Bergianuni the plant is very small and the sporangia 
are reduced in number to a dozen or less. The sterile segment 
is inserted very far down. A most remarkable form has been 
recently described from Sumatra (Bower (20) ). This species, 
O. simplex, is described as having no sterile leaf-segment, or the 
merest rudiment of one, the sporophyll being a flattened slender 
body, with the sporangia closely resembling those of O. pen- 
dulum, to which 0. simplex seems to be allied. O. simplex 
may be considered to represent the most primitive type of the 
genus yet discovered. 

BOTRYCHIUM 

The genus Botrychium includes several exceedingly variable 
species, the simplest forms, like B. simplex (Fig. 141, A, B), 
being very close to Ophioglossum, while leading from these is a 



VII PTERIDOPHYTA—FILICINEJE—OPIIIOGLOSSACEJE 250 

series ending in much more complicated types, of which B. Vir- 
giniannm is a good example. In B. simplex the lamina of the 
leaf is either entirely undivided, as in most species of Ophioglus- 
siiiji, or once pinnatitid. From these there is a complete series 
to the ample decompound leaf (jf B. Virgiiiianiim. When the 
other parts of the plant are studied we find that this greater com- 
plexity extends to them as well. Thus the sporangiophore is 
also decompound, and the sporangia entirely free, showing an 
approach to those of such Ferns as Osmuucla; and the venation, 
wdiich in the simpler forms is dichotomous, approaches the 
pinnate type in B. P^irgiiiianiiiii. The tissues, especially the 
vascular bundles, are also more highly differentiated in the 
larger species. 

Under favourable conditions well-grown plants of B. I'ir- 
ginianuni reach a height of 50 cm. or more, and the sterile 
lamina of the leaf, which is triangular in outline, may be 30 to 
40 cm. in breadth, and from three to four times pinnate. The 
texture of the leaf is membranaceous and not fleshv like that 
of Ophioglossujji and most species of Botrychium. The sporan- 
giophore is twice or thrice pinnate. The plant sends up a single 
leaf each year from the underground stem, which is upright and 
several centimetres in length in old specimens. The roots are 
thick and fleshy, and much smaller at the point of insertion. As 
in Ophioglossuin each root corresponds probably to a leaf, but 
the roots branch frequently, so that the root system is much 
better developed than in Ophioglossuin. The secondary roots 
of B. Viro-inianuiu arise laterallv, and in much the same way as 
those of the higher Ferns. As in the terrestrial species of 
Ophioglossnm, the development of the leaves is very slow. 

In most species of Botrychium the relation of the leaf base 
to the young bud and stem apex is the same as in Ophioglossnm, 
except that the sheath is more obviously formed from the leaf 
base ; but in B. V ir ginianum the sheath is open on one side, and 
more resembles a pair of stipules. Fig. 142, A shows the stem 
and terminal bud of a plant of this species with all but the base 
of the leaf of the present year cut away, and B the same with the 
bud cut open longitudinally. At this stage the parts of the 
leaf for the next year are well advanced, and the formation of 
the individual sporangia just begim. The leaf for the second 
year already shows the sporangiophore clearly evident, and the 
leaf which is to unfold in three years is evident, but the sporan- 




Fig. 141. — A, B, Botrychium simplex, slightly enlarged; C, B. ternatum, X % 5 D, leaf 
segment of B. lunaria; E, leaf segment of B. Virginianum, natural size; F, portion 
of sterile leaf segment of Helminthostachys Zeylanica; G, fragment of the sporan- 
giophore of the same enlarged. A, B, C after Luerssen; D, F after Hooker. 



VII P TERIDOPH Y TA—FILICINE/E—0 PIIIOGLOSSA CEAB 261 

giophore not yet differentiated. At the base of the youngest 
leaf is the stem apex. The wliole bnd is covered in this species 
with numerous short hairs, which are also found in B. tcrnatum 
and some other species ; but in B. simplex and the other simpler 
species it is perfectly smooth, as in Ophiof^lossuiii. The young 
leaves in B. Virginianuni are bent over, and the segments of the 
leaf are bent inward in a way that recalls the vernation of the 
true Ferns. The sporangiophore grows out frrjin the inner 
surface of the lamina, and its branches are directed in the 
opposite direction from those of the sterile part of the leaf. 

B. 




Fig. 142. — Botrychium Virginianum. A, Rhizome and terminal bud of a strong plant, 
the roots and all but the base of the oldest leaf removed, X i ; B, longitudinal sec- 
tion of the bud, X3; st, the stem apex; I. II. III., the leaves; C, transverse sec- 
tion of the petiole, X4; D, transverse section of the rhizome, X about 16; P, 
the pith; m, medullary rays; x, xylem; c, cambium; ph, phloem; sh, endodermis. 

The vascular bundles of the stem are much more prominent 
than in Ophioglossum, and form a hollow cylinder, with small 
gaps only, corresponding to the leaves. This cylinder shows 
the tissues arranged in a manner that more nearly resembles the 
structure of the stem in Gymnosperms or normal Dicotyledons 
than anything else. Surrounding the central pith (Fig. 142, P) 
is a ring of woody tissue (.r) with radiating medullary rays 
(m), and outside of this a ring of phloem, separated from the 



262 MOSSES AND FERNS chap. 

xylem by a zone of cambium (c), so that here alone among the 
Ferns the bundles are capable of secondary thickening. The 
whole cylinder is enclosed by a bundle-sheath (endodermis) 
consisting of a single layer of cells. 

The cortical part of the stem is mainly composed of starch- 
bearing parenchyma, but the outermost layers show a formation 
of cork, which also is developed in the cortical portions of the 
roots. 

The free surface of the stem apex is very narrow, and the 
cells about it correspondingly compressed. The apical cell 
(Fig. 143, A, B), seen in longitudinal section, is very deep and 
narrow, but as comparison of cross and longitudinal sections 
shows, has the characteristic pyramidal form, and here there is 
no doubt that only lateral segments are cut off from it. Holle's 
( (i) PI. iv., Fig. 32) figure of Botrychium rutcefolmm closely 
resembles B. Virginianum, and probably the other species will 
show the same form of apical cell. The divisions are decidedly 
more regular in the segments of B. Virginianiim than in Ophio- 
glossum, and can be more easily followed, although here, too, as 
the division evidently proceeds very slowly, it is difficult to trace 
the limits of the segments beyond the first complete set, which 
in transverse section are sufficiently clear. The first division 
divides the segment into an inner and an outer cell, the former 
probably being directly the initial for the central cylinder. The 
outer cell by later divisions forms the cortex, and the epidermis 
which covers the very small exposed surface of the stem apex. 
As in Ophioglossum, it is impossible to determine exactly the 
method of origin of the young leaves, one of which probably 
corresponds to each segment of the apical cell, but as soon as the 
leaf can be recognised as such it is already a multicellular organ. 
It grows at first by an apical cell which seems to correspond 
closely in its growth with that of the stem. From almost the 
very first (Fig. 143) the growth of the leaf is stronger on the 
outer side, and in consequence it bends inward over the stem 
apex. 

The arrangement of the tissues of the fully-developed stem 
shows, as we have seen, a striking similarity to that in the 
stems of many Spermatophytes. The xylem of the strictly 
collateral bundle is made up principally of large prismatic 
tracheids (Fig. 144), whose walls are marked with bordered 
pits not unlike those so characteristic of the Coniferse, but some- 



VII PTERIDOPHYTA—FILICINEAl—OPHIOGLOSSACE^ 263 

what intermediate between these and the elongated ones found 
in most Ferns. The vvahs between the pits are very much 
thickened, and the bottoms of corresponchng pits in the walls of 
adjacent tracheids are separated by a very delicate membrane. 
At intervals medullary rays, one cell thick, extend from the i)ith 
to the outer limit of the xylem. The cells are elongated radially, 
and have uniformly thickened walls and granular contents. 

The phloem consists of large sieve-tubes and similar but 
smaller parenchymatous cells. No bast fibres or sclerenchy- 
matous cells are present. The whole cylinder is bounded by 




Fig. 143. — Botrychium Virginianum. A, Longitudinal section of the stem apex o 
young plant, X260; B, cross-section of a similar specimen; L, the youngest leaf. 



of a 



a single layer of cells somewhat compressed radially, forming 
the endodermis or bundle-sheath. Between the xylem and 
phloem is a well-defined layer of cambium by whose growth the 
thickness of the vascular cylinder is slowly but constantly added 
to, and as a result there is a secondary growth of the stem 
strictly comparable to that of the Dicotyledons. 

The outer layer of the cortex (the epidermis is quite absent) 
develops cork, but not from a definite cork cambium (Holle, 
(i), p. 249). These cork cells arise by repeated tangential 
divisions in cells near the periphery, and have in consequence 
the same regular arrangement seen in similar cells of the higher 
plants. 



264 



MOSSES AND FERNS 



CHAP. 



A cross-section of the petiole of the earliest leaves of the 
young plant shows but a single nearly central vascular bundle, 
but as the plant grows older the number becomes much larger, 
and may reach ten (Luerssen (8), p. 58). In leaves of mod- 
erate size there are usually about four, and these are arranged 
symmetrically. The ground tissue is composed mainly of 
large thin-walled parenchyma and a well-marked epidermis. 
The fibrovascular bundles are arranged in two groups, right and 
left, and where there are four of them the inner ones are the 



O^ 




Fig. 144. — A, Part of a cross-section of the stem bundle of B. Virginianum, X200, — 
lettering as in Fig. 142; B, a portion of the tracheary tissue, showing the peculiarly 
pitted walls, X400. 

larger, and in cross-section crescent-shaped. The xylem occu- 
pies the middle of the section, and is completely surrounded by 
the phloem, i.e., the bundle is concentric, like that of the true 
Ferns. In B. lunaria the bundle has the phloem only perfectly 
developed on its outer side and approaches the collateral form. 
B. ternatum and B. lunaria, while having concentric bundles, 
also have the phloem more strongly developed on the outer side. 
The tracheary tissue is much like that of the stem, but the 
tracheids are smaller and the walls thinner. The smaller tra- 
cheids show reticulate markings. 



VII PTERIDOPHYTA—FIUCINEAI—OPHIOGLOSSACEJE 265 

The phloem is composed also of the same elements, large 
sieve-tubes, arranged in a pretty definite zone next the xylem, 
and smaller cells of similar appearance, but not showing the 
multinucleate character or perforated transverse walls of the 
latter. The sieve-tubes are large (Fig. 145), and in longi- 
tudinal section are seen to consist of rows of wide cells with 
either horizontal or oblique division walls. The transverse 
walls separating two members of a sieve-tube are somewhat 
swollen and show small perforations, which are not always 





Fig. 145. — Part ot a vascular bundle from the petiole of B. Virginianum, X245; xy, 
xylem; ph, phloem; s, s, sieve-tubes; B, two sieve-tubes in longitudinal section, 
X490; sp, sieve-plates; n, nuclei. 



easily demonstrated. According to Janczewski (4) these pits 
do not penetrate the membrane between the cells, but Russow's 
(5) assumption that there is direct communication between the 
cells is correct, although difficult to prove. Russow also states 
that callus is present in the sieve-plates of Botrychmm, although 
poorly developed. According to Janczewski the pores are not 
confined to the transverse walls, but may also occur, but much 
less frequently, in the longitudinal walls. The contents of the 



266 



MOSSES AND FERNS 



CHAP. 



sieve-tubes consist of a thin parietal layer of protoplasm in 
which numerous nuclei are imbedded. Little glistening glob- 
ules are also found, especially close to the openings of the pores 
of the sieve-plates. 

The lamina of the sterile segment of the leaf is composed 
of a spongy green mesophyll, more compact on the upper sur- 
face. The epidermal cells show the wavy outlines characteristic 
of the broad leaves of other Ferns, and develop stomata only 
upon the lower side of the leaf. 




Fig. 146. — Botrychium Virginianum. A, Longitudinal; B, transverse sections of the 

root apex, X200; pi, plerome. 



The Root 



The roots arise singly at the bases of the leaves, and in 
older plants branch monopodially. Like those of Ophioglossum 
they have no root-hairs, but the smooth surface of the younger 
roots becomes often strongly wrinkled in the older ones. Sec- 
tions either transverse or longitudinal, through the root tip, 
when compared with those of Ophioglossum, show a very much 
greater regularity in the disposition of the cells. This is less 
marked in B. ternatum, and probably an examination of such 
forms as B. simplex will show an approximation to the condi- 
tion found in Ophioglossum, although Holle's figure of B. luna^ 



VII PTERIDOPHYTA—FILICINEJE—OPHIOGLOSSACEAi 267 

ria shows even greater regularity in the arrangement of the 
apical meristem than is found in B. I iri^ijiicniiiin. A careful 
examination of this point is much to be desired. 

The first wall in the young lateral segment is the sextant 
wall, as in the higher Ferns, and divides the segment into two 
cells of unequal depth. The next wall divides the larger of 
these cells into an inner and an outer one, the former becoming 
the initial of the central plerome cylinder, the outer one, to- 
gether wnth the whole of the smaller semi-segment, giving rise 
to the cortex, in which the divisions are very similar to, but 



Fig. 147. — Tetrarch vascular bundle of the root of B. Virginianum, X85; en, endo- 

dermis; ph, phloem; x, xylem. 

somewhat less regular than in Equisehim and the leptospo- 
rangiate Ferns. As usual in roots of this type, segments are 
also cut off from the outer face of the apical cell, but I have never 
seen, either in B. Virginianum or B. tcrnatum, any indica- 
tion that the growth of the root-cap was due exclusively to the 
development of these segments, as Holle states both for B. 
lunaria and Ophioglossiim vidgatum. In both species of Botry- 
chiiini examined by me the growth of the root-cap was evidently 
due in part to the division of cells in the outer part of the lateral 
segments, so that in exactly median sections there w^as not the 



268 MOSSES AND FERNS chap. 

clear separation of the root-cap from the body of the root that 
is so distinct in Equisetum, for example. 

The central cylinder of the root is bounded by an endoder- 
mis whose limits, however, are not so clearly defined as in the 
more specialised Ferns. The number of xylem and phloem 
masses varies, even in the same species. In B. Virginianum 
the larger roots show three or four xylem masses (Fig. 147). 
B. ternatum^ has usually a triarch bundle, while B. lunaria is 
commonly diarch (Holle (i), p. 245). The elements both of 
the xylem and phloem are much like those in the stem and do 
not need any special description. The roots increase consider- 
ably in diameter as they grow older, but this enlargement does 
not take place at the base, where the root is noticeably con- 
stricted. The enlargement is due entirely to the cortical tissue, 
and is mainly simply an enlargement of the cells. The diameter 
of the central cylinder remains the same after it is once formed. 
In the outer part of the root, as in the stem, there is a develop- 
ment of cork. 

The Sporangium 

In the simplest forms of B. simplex the sporangia, which 
are much larger than those of 5. Virginianum, form two rows 
very much as in Ophioglossum; but in all the more complicated 
forms the sporangiophore branches in much the same way as 
the sterile part of the leaf, and the ultimate segments become 
the sporangia. In B. Virginianum the development of the 
individual sporangia begins just about a year previous to their 
ripening, and if the plants are taken up about the time the 
spores are shed, the earliest stages may be found. The sporan- 
giophore is at this time thrice pinnate in the larger specimens, 
and an examination of its ultimate divisions will show the 
youngest recognisable sporangia. These form slight elevations 
growing smaller toward the end of the segment (Fig. 148), 
and exact median sections show that at the apex of the broadly 
conical prominence which is the first stage of the young sporan- 
giumi there is a large pyramidal cell with a truncate apex. 
Holtzman (i) thinks the sporangium may be traceable to a 
single cell, and that the divisions at first are like those in a 
three-sided apical cell. I was unable to satisfy myself on this 

* B. ternatum = B. obliquum (Underwood (5) p. 72). 



vii PTERIDOPHYTA—riLICINEAl—OPHIOGLOSSACEAl 269 

point, but the youngest stages found by me in whicli the 
sporangial nature of the outgrowths was unmistakable, would 
not forbid such an interpretation, althougli there was no doubt 
that the basal part of the sporangium is derived in part from the 
surrounding tissue. 

From the central cell, by a periclinal wall, an inner cell, 
the archesporium, is separated from an outer one. The outer 
cell divides next by cross walls, and this is followed by similar 
divisions in the inner cells (Fig. 148). The succeeding divi- 




FiG. 148. — Botrychium Virginianum. Development of the sporangia. A, i, 2, 
Very young sporangia; B, a somewhat older one, X480; C, older sporangium, 
X240; all median longitudinal sections, the sporogenous cells are shaded. 



sions in the outer cells are now mainly periclinal, and transform 
the four cells lying immediately above the archesporium into 
as many rows of tabular cells. Growth is active in the mean- 
time in the basal part of the sporangium, which projects more 
and more until it becomes almost spherical. To judge from 
the account given by Goebel (3) and Bower (16) oi B. hinaria, 
this species corresponds closely in its early stages to B. Vir- 
ginianmn. The later divisions in the archesporium do not 
apparently follow any definite rule, but divisions take place 
in all directions until a very large number of cells is formed. 



270 MOSSES AND FERNS chap. 

The cells immediately adjoining the sporogenous tissue divide 
into tabular cells, some of which contribute to the tapetum, 
which is to some extent, at least, derived from the outer cells of 
the sporogenous complex, as in Ophioglossum. (See also 
Goebel (22) p. 758). The sporangium shortly before the 
isolation of the spore mother cells (Fig. 148 C) is a nearly glob- 
ular body with a thick, very short stalk. The central part of the 
upper portion is occupied by the sporogenous tissue surrounded 
by a massive wall of several layers of cells. The central cells, 
as usual, have larger nuclei, and more granular contents than the 
outer ones. The stages between this and the ripe sporangium 
were not seen, so that it cannot be stated positively whether all 
the cells of the definitive sporogenous tissue (which seems 
probable) or only a part of them, as in Ophioglossum, develop 
spores. The wall of the ripe sporangium has 4-6 layers of cells, 
and sometimes the place of dehiscence is indicated, as in Ophio- 
glossum, by two rows of smaller cells (Fig. 148, C). 

The stalk is traversed by a short vascular bundle, which is 
first evident about the time that the number of sporogenous 
cells is complete, and joins directly with the young vascular 
bundle of the leaf segment (Fig. 148, C) . The ripe sporangium 
opens by a transverse slit, as in Ophioglossum. 

The presence of fungous filaments in the roots of the 
Ophioglossacese has been repeatedly observed, and has been the 
subject of recent investigations by Atkinson (2), who is inclined 
to regard them as of the same nature as the mycorhiza found 
in connection with the roots of many Dicotyledons, especially 
Cupuliferge. Atkinson asserts that he finds them invariably 
present in all the forms he has examined ; but Holle ( i ) states 
that, while they are usually present in Ophioglossum, he has 
found strong roots entirely free from them, and that in Botry- 
chium riitcrfolium they were mainly confined to the diarch roots, 
and that this is connected with a weakening of the growth of 
the root through the growth of the fungus, by which the triarch 
bundle of the normal fully-developed root is replaced by the. 
diarch form of the weaker one. 

Helminthostachys 

The third genus of the Ophioglossacese, Helminthostachys, 
with the single species H. Zeylanica, is in some respects inter- 



VII PTERIDOPHYTA-FILlCINEAi-OPHIOGLOSSACEJE 271 

mediate between the other two, but differs from both in some 
particulars. The sporophyte has a creeping fleshy subterranean 
rhizome, with the insertion of the leaves corresponding to Opliio- 
glosswn pendulum. According to Prantl (7), who has made a 
somewhat careful study of a plant, the roots do not show any 
definite relation to the leaves, as Holle claims is the case in the 
other genera. The plant sends up a single leaf, which may 
reach a height of 30 to 40 cm. or more, and as in the Opliio- 
glossiim z'ulgatimi and B. V ir giniannm , the sporangiophore 
arises from the base of the sterile division of the leaf. Hie 
latter is ternately lobed, and the primary divisions are also 
divided again. The venation is different from that of the other 
Ophioglossacese, and is extremely like that of Angioptcris or 
Dancca. Each pinnule is traversed by a strong midrib, from 
which lateral dichotomously branched veins run to the margin. 
In regard to the structure of the sheath that encloses the young 
leaf and stem apex, Hehninthostachys resembles Bofrychiuni. 

The apex of the stem, as in the other genera, grows from a 
single initial cell. The stem has a single axial stele, with the 
form of a hollow cylinder, interrupted upon the upper side by 
the leaf-gaps. In the youngest stems, the stele is solid. There 
is an imperfect inner, and a distinct outer endodermis. The 
xylem is mesarch — i. e., it begins to develop in the center of the 
bundle — and its differentiation goes on very slowly. There is 
no formation of secondary wood as in the larger species of 
Botrychium. (Farmer (6)). 

The sieve-tubes have sieve-plates on their lateral faces, and 
similar sieve areas occur upon the walls of the adjacent phloem 
cells. The metaxylem has bordered pits, apparently similar to 
those of Botrychium Virginianum. 

The roots resemble those of Botrychium. There are from 
three to seven xylem masses. 

The sporangiophore is long-stalked and in general appear- 
ance intermediate between that of the other genera, but a careful 
examination shows that it is much more like that of Botrychium. 
It is pinnately branched, but in an irregular way, and the small 
branchlets bear crowded oval sporangia, which open longi- 
tudinally on the outer side, and not transversely as in the other 
genera. The tips of the branches, instead of forming sporangia 
as in Botrychium, develop into green leaf-like lobes, which upon 
the shorter branchlets are often arranged in a rosette of three or 



272 MOSSES AND FERNS chap. 

four together, with the sporangia close below them (Fig. 141, 
D). This at first sight looks as if the sporangia were produced 
upon the lower side of these, like Equisetum, but a very slight 
examination shows at once that this is only apparent, and the 
sporangia are undoubtedly outgrowths of the branches as in 
Botrychium. The green lobes are seen to be only the vegetative 
tips of the branches, or perhaps better comparable to such sterile 
leaf segments as are not uncommon in Osmunda Claytoniana. 
(lower (17), Goebel (22), p. 664.) 

The sporangiophore in Helminthostachys originates as in 
the other genera, and is bent over and protected by the sterile 
leaf-segment, very much as in Botrychium. There is a certain 
correspondence between the early stages of the sporangiophore 
of Helminthostachys and that of Ophioglossum, but in the 
former there are later developed short lateral outgrowths, or 
secondary sporangiophores, which bear clusters of sporangia 
more like those of Botrychium, but the pinnate form of the 
sporangiophore is much less evident. 

The young sporangia project less than those of Botrychium, 
but otherwise closely resemble them. The archesporium is 
referable to a single mother-cell, but the tapetum is derived from 
the surrounding tissue, and not from the primary archesporium, 
as in Ophioglossum. Some of the sporogenous cells, as in 
Ophioglossum, become broken down. 



CHAPTER VIII 

MARATTIALES 

The Marattiace^ 

The Marattiacese, the sole existing family of the order, at the 
present time includes five known genera, with about twenty- 
five species of tropical and sub-tropical Ferns. Many fossil 
types are known which evidently were related to the Marat- 
tiacese, and they seem to comprise the majority of the Palaeo- 
zoic Ferns. 

Recently a good deal of attention has been paid to these 
Ferns, and our knowledge of their life-history and structure is 
fairly complete. Some of them are plants of gigantic size. 
Thus the stem of Angiopteris evecta is sometimes nearly a metre 
in height and almost as thick, with leaves 5 to 6 metres in length, 
and some species of Marattia are almost as large. The other 
genera, Kaiilfiissia, Archangiopteris and Dancca, include only 
species of small or medium size. While in the structure of the 
tissues and the character of the sporangia these show some 
resemblances to the Ophioglossacese, their general appearance is 
more like that of the true Ferns, with which they also agree in 
the circinate vernation of their leaves. The sporangia are borne 
upon the lower surface of ordinary leaves, as in most lepto- 
sporangiate Ferns, but the sporangia themselves are very differ- 
ent, and are more or less completely united into groups or 
synangia, which open either by longitudinal slits or, in Dancea, 
by a terminal pore. The base of the leaf is provided with a 
pair of fleshy stipules, which possibly correspond to the sheath 
at the base of the petiole in Botrychium. 
18 273 



274 MOSSES AND FERNS chap. 

The Gametophyte 

The germination of the spores and development of the 
prothalhum were first investigated by Luerssen (5) and Jonk- 
man (i) in Angiopteris and Marattiaj and later by the latter 
investigator for Kaulfussia (2). More recently Brebner (i) 
has described the prothallium and embryo in Dancea. 

The spores are of two kinds, bilateral and tetrahedral, but 
the former are more common. They contain no chlorophyll, 
but oil is present in drops of varying size, as well as other 
granular bodies. The nucleus occupies the centre of the spore 
and is connected with the wall by fine protoplasmic filaments. 
The wall of the spore is colourless and shows three coats, of 
which the outer one (perinium) is covered with fine tubercles. 

Germination begins within a few days and is first indicated 
by the development of chlorophyll. This does not, as Jonkman 
asserts, first appear in amorphous masses, but very small, 
faintly-tinted chromatophores are present between the large oil- 
drops, and rapidly increase in size and depth of colour as ger- 
mination proceeds, their number increasing by the ordinary 
division. In the bilateral spores the exospore is burst open 
above the thickened ventral ridge found in these spores, and the 
growing endospore slowly protrudes through this. The spore 
enlarges to several times its original diameter before the first 
division occurs, and forms a globular cell in which the large 
chloroplasts are arranged peripherally. 

The first division takes place about a month after the spores 
are sown, and is perpendicular to the longer axis of the cell, 
dividing it either into two equal parts, or the lower may be 
much smaller and develop into a rhizoid. In the former case 
each cell next divides by walls at right angles to the first, and 
the resulting cells are arranged like the quadrants of a circle, and 
one of these cells becomes the two-sided apical cell from which 
the young prothallium for a long time grows (Fig. 149), much 
as in Aneura. This type of prothallium, according to Jonkman, 
is commoner in Marattia than in Angiopteris^ where more com- 
monly a cell mass is the first result of germination. This latter 
is usually derived from the form where a rhizoid is developed 
at first. In this case only the larger of the primary cells gives 
rise to the prothallium. In the larger cell, divisions take place 
in three directions and transform it into a nearly globular cell 



VIII 



MARATTIALES 



'/o 



mass, terminated by four quadrant cells, one of which usually 
becomes the apical cell, much as in the flat prothallium. In 
exceptional cases the first divisions are in one plane and a short 
filament results. 

As soon as the apical cell is established it ^rows in precisely 
the same way as the similar cell in the tliallus of a Liverwort, 
and produces a thallus of much the same f(jrm and structure. 
As the prothallium grows older, however, a cross-wall forms in 




Fig. 149. — Angiopteris evecta. Germination of the spores, — A, B, X220; C, X175; 
sp, spore membrane; x, apical cell (after Jonkman), 



the apical cell, and this is followed by a longitudinal wall in the 
outer one, forming two similar cells wdiich, by further longi- 
tudinal divisions, may produce a row of marginal initials, and 
the subsequent growth of the prothallium is due to the divisions 
and growth of this group of initial cells (Fig. 150, A). 

At first the prothallium has a spatulate form, but before the 
single apical cell is replaced by the group of marginal initials, 
the outer cells of the segments grow more rapidly than the 
inner ones, and the segments project beyond the apical cell, 



276 



MOSSES AND FERNS 



CHAP. 




which comes to lie in a depression between the two lobes formed 
by the outer parts of the segments, and the prothallium assumes 
the heart-shape found in most homosporous Ferns. The sec- 
ondary initial cells vary in number with the width of the inden- 
tation in which they lie. Seen from the surface they are oblong 
in shape, but in vertical section are nearly semicircular (Fig. 
150, B). Basal segments are cut off by a wall that extends 
the whole depth of the prothallium, and the segment is then 
divided by a horizontal wall into a dorsal and ventral cell of 
nearly equal size. The divisions are more numerous in the 

ventral than in the dorsal 
cells of the segment, this 
difference first being mani- 
fest some distance back of 
the apex. Owing to this, a 
strongly projecting, nearly 
hemispherical cushion - like 
mass of tissue is formed 
upon the ventral surface. 
The superficial cells of both 
sides of the prothallium have 
a well-marked cuticle. Nu- 
merous brown rhizoids, 
which, like those of the sim- 
pler Liverworts, are uni- 
cellular and thin - walled, 
grow out from the cells of 
the lower surface, especially 
from the broad midrib. The 
full-grown prothallium in 
M. Douglasii is sometimes a 
centimetre or more in length 
(Fig. 151), and tapers from the broad heart-shaped forward 
end to a narrow base. In Angiopteris (Farmer (3) ) it is more 
nearly orbicular. In both genera it is dark-green in colour, 
looking very much like the thallus of Anthoceros IcBvis, and like 
this too is thick and fleshy in texture. A broad midrib extends 
for nearly the whole length of the thallus and merges gradually 
into the wings, which are also several-layered, nearly or quite 
to the margin. 

The prothallium of Dancea (Brebner (i)) resembles more 




Fig. 150. — Marattia Douglasii. A, Horizon- 
tal section of prothallium apex, with two 
initials, Xi6o. B, Longitudinal section 
of a similar growing point; d, dorsal; v, 
ventral segment. 



VIII 



MARATTIALES 



277 



closely that of Angiopteris, than that of Marattia. The rhizoids 
are miilticeHular, recalhn^ those of the ^ametophyte of 
Botrychinm. 

The very old prothalHa sometimes hranch dichotomously 
(Fig. 151, B, C), and the process is identical with tliat in the 
thallose Hepatic?e. The two growing points are separated by 
a median lobe in the same way, and the midrib with the sexual 



B 




X. . .1 ■>•.•.-■ ..• 












Fig. 151. — Marattia Douglasiu A, Prothallium about one year old, X2; B, the same 
prothallium about a year later, showing a dichotomy of the growing point; C, the 
same seen from below, showing two archegonial cushions (^) ; D, prothallium with 
young sporophyte, X4; E, a somewhat older one, seen from the side; r, the pri- 
mary root. 



organs upon It forks with it, exactly as we find, for example, 
the antheridial receptacle forking in Fimbriaria Californica 
(Fig. I, A). Besides this form of branching, which is not 
common, adventitious buds are produced upon the margin of 
the thallus very frequently. These grow^ in precisely the same 
way as the main prothallium, and after a time may become 



278 MOSSES AND FERNS chap. 

detached and form independent plants; or they may develop 
sexual organs (mainly antheridia) while still connected with 
the mother plant. The duration of the prothallium is apparently 
unlimited, so long as it remains unfecundated. The writer 
kept prothallia of Marattia Douglasii for nearly two years, 
during which they grew continuously and finally reached a 
length of over two centimetres. At the end of this time they 
were growing vigorously, and there was nothing to indicate the 
slightest decrease in their vitality. 

The prothallia are monoecious, although not infrequently 
the smaller ones bear only antheridia. The latter always 
appear first, and are mainly found upon the lower side of the 
midrib, but may also occur upon the upper side. The arche- 
gonia are confined to the lower surface of the midrib, and as 
they turn dark brown if they are not fertilised, they are visible 
to the naked eye as dark brown specks studding the broad thick 
midrib. Both antheridia and archegonia resemble closely those 
of Ophioglossiim. 

The Sex-organs 

The antheridium arises from a single superficial cell which 
first divides into an inner cell, from which the sperm cells are 
derived, and an outer cover cell (Fig. 152, A). The latter 
divides by several curved vertical walls (Figs. E-G) which 
intersect, and the last wall cuts off a small triangular cell (0), 
which is thrown off when the antheridium opens, and leaves 
an opening through w^hich the sperm cells are ejected. The 
inner cell, by repeated bipartitions, gives rise to a large number 
of polyhedral sperm cells. Before the full number of these is 
complete, cells are cut off from the adjacent prothallial cells, 
which completely enclose the mass of sperm cells. As in other 
Archegoniates, the nucleus of the sperm cell, after its final 
division, shows no nucleolus. The first sign of the formation 
of the spermatozoid that could be detected was an indentation 
upon one side, followed by a rapid flattening and growth of the 
whole nucleus. The cytoplasmic prominence which, according 
to Strasburger, is the first indication of the formation of the 
spermatozoid, could not be certainly detected. The main part 
of the spermatozoid, stains strongly with alum-cochineal, and 
is sharply differentiated against the colourless cytoplasm, and 



VIII 



MARATTIALES 



279 



for some time shows the characteristic nuclear structure. The 
origin of the ciha was not clearly made out, but there is little 
question that they arise from a blepharoplast as in (jther cases 
that have been more recently investigated. The free sperma- 
tozoid (Fig. 152, I), is a flattened band, somewhat blunt behind 
and tapering to a fine point in front; attached to a point just 
back of the apex are several fine cilia. The body shows only 
about two complete coils. 




Fig. 152. — Marattia DouglasU. Development of the antheridium. A-D, Longitudinal 
section, X515; E-G, surface views, X257; H, ripe sperm cells; I, free spermato- 
zoids, X1030; 0, operculum. 



The youngest archegonia are met w^ith some distance back 
of the growing point, and apparently any superficial cell is 
potentially an archegonium mother cell. The latter divides 
usually into three superimposed cells (Fig. 153, A), of which 
the lowest (b) forms the base of the archegonium. The basal 
cell, however, may be absent in Marattia Douglasii, as is also 
the case in Angiopteris and Dancea. From the middle cell by a 
transverse division are formed the primary neck canal cell and 



280 



MOSSES AND FERNS 



CHAP. 



the central cell. Each of these divides again transversely. In 
the upper one this division is often incomplete and confined to 
the nucleus; but in the central cell the division results in the 
separation of the ventral canal cell from the ovum. Before the 
separation of the primary neck canal cell from the central cell, 
the cover cell divides as in the Liverworts into four cells by 
intersecting vertical walls, and each of these cells by further 
obliquely transverse walls forms a row of about three cells, and 
these four rows compose the short neck. The canal cells are 




Fig. 153. — Marattia Douglasii. A-D, Development of the archegonium, X4S0; E, sec- 
tion of the fertilised egg, showing the spermatozoid (sp) in contact with its nu- 
cleus, X485; F, successive longitudinal sections of a young embryo, X225; b, b, 
the basal wall; the arrow points towards the archegonium. 



very broad and the ^gg cell small, so that after the archegonium 
opens it occupies but a small part of the cavity left by the 
disintegration and expulsion of the canal cells. Before the 
archegonium is mature, flat cells are cut off from the adjacent 
prothallial tissue as in the antheridium (Fig. 153, D). The 
neck of the ripe archegonium projects but little above the 
surface of the prothallium, and in this respect recalls both the 
lower Ophioglossaceae and the Anthocerotes. The ripe ovum 
is somewhat elliptical, and slightly flattened vertically. Its 



VIII 



MARATTIALES 



281 



upper third is colourless and nearly hyaline. This is the 
''receptive spot," and it is here that the spermatozoid enters. 
The nucleus is of moderate size, and not rich in chromatin; a 
small but distinct nucleolus is present. The spermatozoid 
retains its original form after it first enters the egg, and until it 
comes in contact with the membrane of the egg nucleus. It 
afterwards contracts and assumes much the ap])earance of the 
nucleus of the sperm cell previous to the differentiation of the 
spermatozoid. The two nuclei then gradually fuse, but all the 
different stages could not be traced. Before the first division 

A. 




Fig. tftA'-^-Marattia Douglasii. Embryogeny. A, Longitudinal; B, transverse sections 
of embryos, X215; C, vertical section of an older embryo, showing its position in 
the prothallium, X72; st, the stem; pr, prothallium; D, upper part of the same 
embryo, X215. 

takes place, however, but one nucleus can be seen, and this 
much resembles the nucleus of the unfertilised egg. It is prob- 
able that the nucleus of the spermatozoid really penetrates the 
cavity of the egg-nucleus as has been shown to be the case in 
Onoclea. ( See Shaw ( i ) ) . 

The Embryo — (Farmer (3) ; Jonkman (s)) 
After fertilisation the egg enlarges to several times its 
original size before dividing. The first (basal) wall is trans- 



282 



MOSSES AND FERNS 



CHAP. 



verse and is followed in each half by two others, the median and 
octant walls. The nearly globular embryo is thus divided into 
eight similar cells, each having the tetrahedral form of a globe 
octant. The next divisions are not perfectly understood, and 
evidently are not absolutely uniform in all cases. All the 
octants at first show nearly uniform growth, and the embryo 
retains its nearly oval form (Figs. 153, F, 154, A). The first 
division in the octants is essentially the same, and consists in a 
series of anticlinal walls, before any periclinal walls appear, so 
that we may say that for a short time each octant has a distinct 
apical growth, and there are eight growing points. The older 




Fig. 155. — Marattia Douglasii. A, Cross-section of the young sporophyte at the junc- 
tion of the cotyledon and stem; st, the apical meristem of the stem, X215; B, the 
stem apex of the same, X430; C, longitudinal section of the stem apex of a plant 
of about the same age, X21.S; tr, the primary tracheary tissue; r^, the second 
root. 



embryo shows an external differentiation into the first leaf, 
stem, and root, but the foot is not clearly limited at first. The 
basal wall separates the embryo into two regions, epibasal and 
hypobasal. From the former the cotyledon and stem apex 
are derived, from the latter the root and foot. 

The cotyledon arises from the anterior pair of epibasal 
octants, which are in the Marattiacege, unlike all the other Ferns, 
turned away from the archegonium opening. In the earliest 
stages where the cotyledon is recognisable, no single apical cell 
could be made out, and later the growth is very largely basal. 



Vlll 



MARATTIALES 



283 



At first the growth is nearly vertical, but it soon becomes 
stronger upon the outer side, and the leaf rufliment bends 
inwards. At this stage the dififerent tissues begin to l>e dis- 
tinguishable. Somewhat later the tip of the cotyledon becomes 
flattened, and still later there is a dichotomy of this flattened 
part which thus forms a fan-shaped lamina (Fig. 157). The 




Fig. 156. — Marattia Douglasii. A, B, C, Three transverse sections of a root from the 
young sporophyte; A shows the apical cell (x), X215; D, longitudinal section of a 
similar root, X260; E, vascular bundle of the root, X260. 



first tissue to be recognised is the vascular bundle w^hich 
traverses the centre of the petiole and at first consists of uni- 
form thin-walled elongated cells (procambium). This forma- 
tion of procambium begins in the centre of the embryo and 
proceeds in three directions, one of the strands going into the 



284 MOSSES AND FERNS chap. 

cotyledon, one in an almost opposite direction to the primary 
root, and a very much shorter one to the young stem apex, 
which lies close to the base of the cotyledon. The outer layer 
of cells of the cotyledon forms a pretty clearly defined epidermis 
separated from the axial procambium strand by several layers 
of young ground-tissue cells. 

The apex of the young stem is occupied in some cases, at 
least, by a single apical cell, which probably is to be traced back 
directly to one of the original octants of the embryo. Whether 
this is always the case in the youngest stages cannot be de- 
termined until further investigations are made. Farmer (3) 
was unable to make out a single initial in Angiopteris, which 
otherwise agrees closely with Marattia. Dancea, according to 
Brebner ( i ) , shows a single initial cell at the stem-apex, as well 
as that of the primary root. 

The study of the root was confined mainly to the older 
embryos, and although some variation is noticed, it is pretty 
certain that there is a single apical cell, not unlike that found 
in the Ophioglossacese. Whether this can be traced back to 
one of the primary hypobasal octants, it is impossible now to 
say; but Farmer's statement that in Angiopteris there is at first 
a three-sided apical cell would point to this. Unfortunately 
my own preparations of Marattia were too incomplete to decide 
this point in the latter. In the older root the form of the apical 
cell was usually a four-sided prism, from all of whose faces 
segments were cut off, although sometimes an approach to the 
triangular form found in the Ophioglossacese was observed. 

The foot is much less prominent than in Botrychium, and 
in this respect the Marattiacese are more like Ophioglossum 
(Mettenius (2), PL xxx). In Marattia all the superficial cells 
of the central region of the embryo become enlarged and act as 
absorbent cells for the nourishment of the growing embryo. 

As the embryo grows, the surrounding prothallial tissue 
divides rapidly, and a massive calyptra is formed which com- 
pletely encloses the young sporophyte for a long time. Owing 
to the position of the cotyledon and stem, which grow up 
vertically through the prothallium, a conspicuous elevation is 
formed upon its upper side, through which the cotyledon finally 
breaks, A similar elevation is formed by the calyptra upon 
the lower side, through which the root finally penetrates, but not 
until after the cotyledon has nearly reached its full development. 



VIII 



MARATTIALES" 



285 



The proihallium does not die immediately after the young 
sporophyte becomes independent, but may remain aHve for 
several months afterwards, much as in Botrychiiim. 

The first tracheary tissue arises at the junction of the bun- 
dles of the cotyledon, stem, and root. These primary tracheids 
are short and their walls are marked with reticulate thickeninj:j^s. 
From this point the development of the tracheary tissue, as well 
as the other elements of the bundles, proceeds toward tlie a])ices 
of the young organs. The formation of the secondary 
tracheids is always centripetal. 




Fig. 157. — A, Young sporophyte of Danaea simplicifolia, still attached to the gameto 
phyte, pr; X3; B, an older sporophyte of the same species; C, gametophyte of 
Angiopteris evecta, with the young sporophyte. (A, B, after Brebner; C, after 
Farmer.) 

Jeffrey (3) states that in the young sporophyte of several 
species of Dancea examined by him, the stele has the form of a 
tube with both internal and external endodermis and phloem. 
Both internal endodermis and phloem tend to disappear in the 
later-formed part of the stem. The tubular central cylinder is 
interrupted by the foliar gaps, and later there are formed 
medullary vascular strands, and the vascular system gradually 
assumes the very complicated form met with in the older 
sporophyte. Brebner (3) states that in Dancea simplicifolia the 



286 MOSSES AND FERNS chap. 

primary vascular axis is a .simple concentric stele, which is later 
replaced by a cylindrical stele like that of D. alata. 

Short hairs with cells rich in tannin, and staining strongly 
with Bismarck-brown, occur sparingly upon the leaves and 
stem of the young sporophyte. 

The fully-developed cotyledon has the fan-shaped lamina 
somewhat lobed, and the two primary veins arising from the 
forking of the original vascular bundle usually fork once more, 
so that the venation is strictly dichotomous in character. The 
nearly cylindrical petiole is deeply channeled upon the inner 
side, and the single axial vascular bundle is almost circular in 
section. While the crescent-shaped mass of tracheary tissue is 
completely surrounded by the phloem, the latter is much more 

strongly developed 
upon the outer side, 
and the bundle ap- 
proaches the collateral 
form of Ophioglos- 
sum. Indeed, if the 
tannin cells, which are 
found here, belong to 
the cortex, as Farmer 
asserts to be the case 
in Angiopteris, the 
bundle would be truly 
17 ^ Q XT • ^ 1 .• f .1, 1 • * .T, collateral, as these tan- 

riG. ISO. — Horizontal section of the lamina of the _ ' 

cotyledon of M. Dougiasii, X260. uin ccUs are immedi- 

ately in contact with 
the tracheids. The lamina of the cotyledon is similar in struc- 
ture to that of the later leaves, and differs mainly in the smaller 
development of the mesophyll. The smaller veins have the 
xylem reduced to a few (1-3) rows of tracheids upon the 
upper side of the collateral bundle. Stomata of the ordinary 
form occur upon the lower side of the leaf. 

In Angiopteris (Fig. 157, C) and Dancea (Fig. 157, A), 
the cotyledon is spatulate in outline with a distinct midrib. 

As the root finally breaks through the calyptra and pene- 
trates into the earth, numerous fine unicellular root-hairs 
develop from the older parts, but the tip for some distance 
remains free from them. Owing to the numerous irregularities 
in the cell divisions, the exact relation of the tissues of the 




VIII 



MARATTIALES 



287 




■F. 



older parts of the root to the sei^mcnts of the apical cell is 

impossible to determine, and evidently is not always exactly 

the same. The root-cap is derived mainly from the outer 

segments of the apical cell, but also to some extent from the 

outer cells of the lateral segments; and the central cylinder, 

where the base of the 

apical cell is truncate, is ^^ \. St A. 

formed mainly from the 

basal segments, but in 

part as well from the 

inner cells of the lateral 

segments. 

The vascular cylin- 
der of the root is usually 
tetrarch. At four points 
near the periphery small 
spiral or annular 
tracheids appear, and 
from them the formation 
of the larger secondary 
tracheids proceeds 
toward the centre. The 
phloem is made up of 
nearly uniform cells with 
moderately thick colour- 
less walls. A bundle- 
sheath is not clearly to be 
made out (Fig. 156). 

The cotyledon is des- 
titute of the stipules 
found in the perfect 
leaves of the Marat- 




FlG. 



159. — Marattia Douglasii. A, Longitudinal 
section of the young sporophyte, showing the 
distribution of the vascular bundles, X6; /, 
leaves; st, stem apex; r, a root; f, the foot; 
B, young sporophyte with the prothallium 
(pr), still persisting. 



tiaceae, but they are well 
developed in the third 
leaf, where they form 
two conspicuous append- 
ages clasping the base 

of the next youngest leaf. The edges of these stipules are 
somewhat serrate, and the edges of the two meet, much like two 
bivalve shells. The strictly dichotomous character of the 
cotyledon is gradually replaced in the later leaves by the pinnate 



288 



MOSSES AND FERNS 



CHAP. 



arrangement, both of the divisions of the leaf and the venation. 
This is brought about in both cases by an unequal dichotomy, 
by which one branch develops more strongly than the other, 
so that the latter appears lateral. With the assumption of the 
pinnate form the leaf also develops the wings or appendages 
upon the axis between the pinnae. In the fully-developed leaves 
of the mature sporophyte, the last trace of this is seen in the 
ultimate branching of the veins, which is always dichotomous. 
The second root arises close to the base of the second leaf, 
and at first there seems to be one root formed at the base of 
each of the young leaves ; in the older sporophyte the roots are 





Fig. i6o. — A, Longitudinal section; B, transverse section of roots from older sporo« 
phyte of M. Douglasii, showing apparently more than one initial cell, X200. 



more numerous. Holle states that this is not the case in 
Marattia, where only one root is formed for each leaf, in 
Angiopteris two. This, however, requires confirmation in the 
older plants. As the roots become larger it is no longer pos- 
sible to distinguish certainly a single initial cell. The adjacent 
segments themselves assume to some extent the function of 
initials, and thus in place of the single definite apical cell a group 
of apparently similar initials is formed, which takes its place 
(Fig. 160). This seems to be in some degree associated with 
the increase in size of the roots. ^ 



^ It is possible that a single initial may be present even here, but the 
great similarity of the central group of cells makes this exceedingly difficult 
to determine. 



VIII 



MARATTIALES 



The Adult Sporophyte 



289 



According to Holle (1. c. p. 218) the four-sided apical cell 
found in the stem of the young sporophyte of Marattia is re- 
tained permanently, but in Angiopteris this is not the case, as 
in the older sporophyte a single apical cell is not certainly to be 
made out. Bower ((11) p. 324) comes to the same conclusion 

A, a 




Fig. 161. — A, Section of the stipe of Angiopteris evecta, natural size; B, section of the 
rachis of the ultimate division of the leaf of Marattia alata, X15; *"» mucilage 
ducis; C, collenchyma from the hypodermal layer of the rachis, X250; D, part 
of the vascular bundle of B, X2S0; t, tannin cells. 

as Holle, although in an earlier paper (2) he attributes a single 
apical cell to the stem of Angiopteris. The stem in both genera 
becomes very massive, but its surface is completely covered by 
the persistent stipules. 

The structure of the stem in Angiopteris has recently been 
carefully investigated by Miss Shove ( i ) who has also reviewed 
19 



290 MOSSES AND FERNS CHA'^. 

the earlier literature upon the anatomy of the Marattiacese. In 
the stem of Angiopteris there is a reticulate vascular cylinder 
like that of Ophioglossum, but within this are three or four 
similar concentrically arranged ''meshed zones," and a single 
central strand. In the specimen examined by Miss Shove the 
stem was oblique, and the meshes of the vascular cylinders were 
much closer upon the dorsal than upon the ventral side. 

The majority of the roots originate from the inner zones, 
but they may also arise from the outer ones. The leaf-traces 
all come from the outer zone — at least such was the case in the 
specimen studied by Miss Shove. It is stated that Mettenius 
(3), found that the leaves also received strands from the second 
vascular zone. The concentric vascular cylinders are connected 
by branches ("compensating segments"), which pass out to 




Fig. 162. — Dancea alata. A, Transverse section of vascular bundle of the petiole, Xi75; 
X, tracheary tissue; t, tannin cells. B, Cross-section of a mucilage duct, Xi7S. 

the gaps formed by the departure of the leaf-traces. Marattia 
(Kiihn (2)), closely resembles Angiopteris in its stem struc- 
ture, but it has but two vascular cylinders outside the central 
strand, while Kaulfiissia has but a single one. The bundles, 
are, according to Holle ( (2), p. 217) concentric, but the phloem 
more strongly developed upon the outer side. 

The thick petioles of the full-grown leaves are traversed by 
very numerous vascular bundles, which at the base give off 
branches that supply the thick stipules within which they 
branch and anastomose to form a network. These bundles in 
Angiopteris (Fig. 161, A) are arranged in several circles, or 
according to De Vriese ( i ) and Harting, the central ones form 
a spiral. In the rachis of the last divisions- of the leaves, how- 



VIII 



MARATTIALES 



291 



ever, both of Maraftia and Angiopteris, there is but a single 
axial bundle, as in the petiole of the cotyledon. 

Fig. 167, B shows a cross-section of a pinnule from a large 
leaf of A. evccta, which has much the same structure as that of 
Marattia. The central vascular bundle is horse-shoe shaped in 
section, and shows a central mass of large tracheids with retic- 
ulate or scalariform markings, surrounded by the phloem made 
up of very large sieve-tubes much like those of Botrychium, 
and with these are the ordinary protophloem cells and bast 
parenchyma. A distinct bundle-sheath is absent, as, according 
to Holle, it is from all the bundles in both Marattia and An- 
giopteris, except those of the larger roots. The bulk of the 




Fig. i63.^A, Section of a large root of Angiopteris evecta, X14; '». mucilage duct; 
B, part of the central cylinder, X about 70; en, endodermis. 

ground tissue is composed of large parenchyma cells, but on 
both sides just below the epidermis is a band of colourless cells 
which resemble exactly the collenchyma of Phanerogams. In 
the base of the petiole this becomes harder and forms a colour- 
less sclerenchyma, which in Dancua is replaced by brown scleren- 
chyma like that of the true Ferns. In the lamina of the leaf in 
Angiopteris too, the arrangement of the tissues is strikingly like 
that of the typical Angiosperms. A highly-developed palisade 
parenchyma occupies the upper part of the leaf beneath the epi- 
dermis, which bears stomata only on the lower side of the leaf. 
The rest of the mesophyll is composed of the spongy green 
parenchyma found in the other Ferns. The smaller veins both 
here and in Marattia have collateral bundles. 



292 MOSSES AND FERNS chap. 

Short hairs occur upon the young sporophyte, and upon the 
older plant there may be developed scales (palese) similar to 
those found in the leptosporangiate Ferns. 

The base of the stipe, as well as that of the rachis of the leaf- 
segments, is enlarged, closely resembling the ''pulvinus" of a 
leguminous leaf. The stalk breaks at this place, leaving a clean 
scar. The smaller leaflets separate in the same way from the 
rachis. 

The Marattiacese all develop conspicuous mucilage ducts 
(Figs. 162, 163, m) and gum canals, very much like those 
occurring in the Cycads (Brebner (2)). These ducts are of 
two kinds. The first type is "schizogenic," i. e., of intercellular 
origin, the secretory cells surrounding the intercellular canal. 
The ducts of the second type are formed from the breaking 
down of rows of tannin-bearing cells, which thus form irregular 
ducts, not unlike certain milk-tubes of the higher plants. 

Upon the stipules and stipe there are often present lenticel- 
like structures ("Staubgriibchen" of German authors). These 
originate beneath stomata, in much the same way as the ordi- 
nary lenticels ; but the cells below the opening of the lenticel are 
not cork-cells, but small, thin-walled cells, which separate and 
dry up, forming a dusty powder. 

Intercellular rod-like organs, composed mainly of calcium- 
pectate, are of common occurrence. There may also occur 
silicious deposits, and crystals of calcium-oxalate have been ob- 
served in Angiopteris (See Bitter (i)). 

The Sporangium 

The sporangia of the Marattiacese differ most markedly 
from the Ophioglossacese in being borne on the lower side of the 
ordinary leaves, and not on special segments. Except in 
Angiopteris, they form synangia, whose development has been 
especially studied in Marattia. Luerssen (7) describes the 
process thus : 'Tn Marattia the first differentiation of the spo- 
rangium begins while the young leaf is still rolled up between the 
stipules of the next older one. The tissue above the fertile vein 
is more strongly developed than the adjoining parenchyma, and 
forms an elevated cushion parallel with the vein. This is the 
receptacle, which develops two parallel ridges, separated by a 
cleft. These two ridges grow up until they meet, and their 
edges grow together and completely close the cleft which lies 



VIII 



MARATTIALES 



293 



between. In each half there are differentiated the separate 
archesporial groups of cells corresponding to the separate 
chambers found in the complete synangium." The whole 
process takes, according to his account, about six months. 
Luerssen was unable either in Marat tia or Augioptcris to trace 
back the archesporium to a single cell, which Goebel (3) claims 
is present in the latter. 

In Angioptcris the process begins as in Marattia, but at a 
period when the leaf is almost completely developed and 




Fig. 164. — Angiopteris evecta. Development of the sporangium. A, Vertical section 
of very young receptacle; B, similar section of an older sporangium in which the 
archesporium is already developed (after Goebel) ; C, longitudinal section of an 
almost fully-developed sporangium, showing the persistent tapetal cells (0 ; r, the 
annulus, X75' 



unfolded. The first indication of the young sorus is the 
formation of an oblong depression above a young vein, and 
about the border of this are numerous short hairs, which as a 
rule are absent from the epidermis of the leaf (Fig. 164, A). 
The placenta is formed as in Marattia, but instead of the two 
parallel ridges that are found in the latter, the young sporangia 
arise separately, much as in Botrychmm. As in the latter too, 
Goebel states that the archesporium can be traced to a single 



294 



MOSSES AND FERNS 



CHAP. 



hypodermal cell in the axis of the young sporangium. This 
cell divides repeatedly, but apparently without any definite 
order, and the division of the spores follows in the usual way. 
From the cells about the archesporium tapetal cells are cut off, 
but these do not disappear, as Goebel (3) asserts, but persist 
until the sporangium is mature. The growth is greater 

upon the outer side, which is 
strongly convex, while the 
inner face is nearly flat. 

A section of the nearly 
f ull-grow^n sporangium ( Fig. 
164, C) shows that the wall 
upon the outer side is much 
thicker, and is composed for 
the most part of three layers 
of cells, of which the outer 
in the ripe sporangium have 
their outer walls strongly 
thickened. The top of the 
sporangium and the inner 
wall are composed of but one 
layer of cells (exclusive of 
the tapetum), which are flat 
and more delicate than those 
upon the outer side. Near 
the top on its outer side is a 
transverse line of cells with 
thickened darker walls, which 
project somewhat above the 
level of the others. This is 
T7 , ,. ^ . ^ . , ^ the annulus or ring, and re- 

xiG. 165. — Marattia fraxmea. A, Transverse ° 

section of young synangium, X225; B, SCmblcS cloSCly that of Os- 

similar section of an older synangium, ^^i^j^da. Lining the Wall is a 
X112; X, X, the tapetal cells. (After ^ 

Bower.) layer of very large thin- 

walled cells which form the 
tapetum. This in Angiopteris remains intact until the spores 
are divided. Whether it disappears before the dehiscence of 
the sporangium was not determined. The contents of these 
cells, which are very much distended, and evidently actively 
concerned in the growth of the forming spores, contain very 
few granules, but are multinucleate in many cases. Whether 




VllI 



MARATTIALES 



295 



this condition is due to a coalescence of originally separate cells, 
or what seems more likely, arises simply from nuclear division 
in the young tapetal cells, without the formation of cell walls, 
was not decided. The young spore tetrads, at this time, are 
embedded in an apparently structureless mucilaginous matter, 
which stains uniformly with Bismarck-brown. This mucilage 
apparently is secreted by the tapetal cells for the nourishment 
of the spores. 

Bower (17) has recently made a very complete study of the 
development of the sporangium in all the genera except 



A. 



B. 





Fig. 166. — A, Transverse section of three synangia of Dancea alata, Xis; B, horizontal 
section of a synangium, showing the numerous loculi, X15; C, vertical; D, hori- 
zontal section of a synangium of Kaulfussia cesculifolia, XiS. (C, D, after 
Bower.) 



Archangiopteris. He finds in all of them that the sporogenous 
tissue of each sporangium (or loculus), can usually be traced 
to a single mother-cell, although there may be exceptions to. this 
rule. 

In all cases the tapetum arises from the tissue adjacent to 
the archesporium, and not from the outer cells of the sporog- 
enous complex. In this respect the Marattiacese resemble more 
nearly Hehninthostachys or Botrychhim than they do Ophio- 
glossum. 

In Dancea and Kaulfussia there is no mechanical tissue rep- 
resenting an annulus. The dehiscence is accomplished by a 



296 



MOSSES AND FERNS 



CHAP. 



CO 




1 

c 


4: 




a 








"i 




"c 






u 


.^ 




-u 




. <u 




•** 


CC 




C) 


n 




V) 


0. 




• • 






^ _- 


•H 


Q 


• 




X 












y^*^ 


X 


i 




i 


O) 


to 


3 






",S) 

:g - 


..& 


. rt 




4^ 


C 


'«4H 


to 


>t 








to 




JS 


^ 


U 


•*J 


"S) 


T3 


60 


c 


"i 


C 


*m 


a 


? 


a 










>** 












-4-t 

(0 


4-> 


do 


u 


s 




Sf 





"rt 
-4-* 


(n 




C 


0) 




*** 





U 


<i4 


'C 




Q 





PQ 





JS 


• *. 


:^ 


w" 


"* 






X 


Ml 




■<1- 


•v 


■M 


X 


C8 


s 




'be 


ji 


CO 


c 


"a 


.Si 


rt 

Wi 



a 

to 


be 



01 
(0 


•4-* 


>> 


i 


■^ 


eS 


rt 

CO 


VM 


B 


lU 


CO 





^ 


o; 


u 


4.» 


wH ^*^ 








SM 


rt 


rt 





M-l 


4i 


M-l 







rt 




U 


^ 


rt 
< 


rt 

e 


13 
0. 

01 




^ 


> 


, 


u 


u 


« 


B 


-S 


Hi^ 


CI 


1 


<J 


u 


>. 


^ 


rt 






a 


3 


•5 


■0 


rt 


»>. 


rt 


<u 


(0 


a 



-w 




<». 


rt 





0. . 


u 


■^ 


<*A 


s 


■^ 


« 


^ 




rt 

p4 


1 


'^ 

e 


bo 

C 
rt 


vo 


>> 


C 


« ja 


!>. 




u 


!0 


d 






w - 






p^ 







VIII 



MARATTIALES 



297 



shrinking of the cells on either side of the opening slit. The 
latter in Dancoa is short, and finally appears like a circular pore, 
but is really not essentially different from that in Kaulfiissia and 
Maraftia. In the latter there is a mechanical tissue which 
causes the two valves of the synangium to gape widely at ma- 
turity, and the dehiscence of the individual loculi is effected by 

A- 




Fig. 168. — Archangiopteris Henryi. A, Entire sterile leaf, reduced; B, base of stipe, 
showing the stipules; C, part of a fertile pinna, of the natural size. (After 
Christ & Giesenhagen.) , 

the contraction of thinner walled cells surrounded by firmer 
tissue. 

The number of spores produced in each loculus is approx- 
imately 1750 for Dancca, 7500 for Kaulfiissia, 2500 for Marat- 
tia, and 1450 for Angiopteris. 

J Bower's account and figures of Angiopteris differ from the 
specimens examined by the writer in the greater thickness of 



298 



MOSSES AND FERNS 



CHAP. 



the sporangium wall. This may have been due to different 
conditions under which the plants were grown, or to a possible 
difference in the species. 

There is frequently found surrounding the synangium, hairs 
or scales which form a sort of indusium (Fig. 165). In 
Dancea, the leaf tissue between the synangia grows up as a 
ridge, with expanded top overarching them. This ridge in sec~ 
tion appears T-shaped (Fig. 166, A). 




Fig. 169. — A small plant of Dancea alata, X5^; st, stipules. 



Classification of the Marattiace^ 



- The living Marattiaceae (Bitter (i)) may be divided into 
four sub-families, of which the first, Angiopteridese includes 
two genera, Angiopteris and Archangiopteris, while the others, 
Marattiese, Kaulfussiese, and Danaease, contains each but a 
single genus. - - 



VIII 



MARATTIALES 



299 



Marattia includes about twelve species of tropical and sub- 
tropical Ferns, both of the Old World and the New. Kaiil- 
fussia includes but a single species, belonging to southeastern 
Asia. The synangia are scattered over the lower surface of 
the palmate leaf, and are circular, with a central space into 
which the separate loculi open by a slit, as in Marattia. Kaiil- 
fussia is characterised by very large pores upon the lower side 
of the leaf. A study of the development of these shows that at 
first they are perfectly normal in form, and that the large round 
opening is a secondary formation, the two guard cells of the 
young stoma being torn apart, and disappearing almost entirely 
in the older leaf. 




Fig. 170. — Dancea alata. A, Sterile; B, fertile pinna, Xi^; C, cross-section near the 
base of the petiole, X6; sel, selerenchyma; m, mucilage ducts; vb, vascular bundles. 



The genus Dancea is exclusively American and comprises 
about fourteen species of small or middle-sized Ferns. D. sini- 
plicifolia has a simple lanceolate leaf, the others have once- 
pinnate leaves. The fleshy stipe is often characterised by con- 
spicuous swellings. The venation of the leaves (Fig. 170) is 
much like that of Angiopteris and some species of Marattia. 
The fertile pinnae are decidedly contracted, and the elongated 
synangia almost completely cover their lower surface. 

The stem (Fig. 169) is a horizontal fleshy rhizome, the 
leaves arranged in tw^o ranks upon the upper side. The leaf- 



300 MOSSES AND FERNS chap. 

base has a pair of conspicuous stipules like those found in the 
other genera. 

Kaulfussia cFsculifolia is the sole representative of the family 
Kaulfussiese, and differs very much in habit from the other liv- 
ing Marattiacese. The rhizome and leaf arrangement are not 
unlike those of Dancea, but the leaf is palmately divided, and the 
venation is reticulate, while the synangia are scattered. The 
synangium is circular, or broadly oval in outline. (Fig. i66). 

The recently discovered Archangiopteris, (Fig. i68) is a 
small Fern from southern China, which in habit resembles 
Dancea. The sporangia, however, are more like those of 
Angiopteris. 

The AMnities of the Eusporangiate Filicinece 

In attempting to determine the affinities of the members of 
this group, many difficulties are encountered. First, and 
perhaps most important, is the small number of species still 
existing, which probably are merely remnants of groups once 
much more abundant. This is certainly true of the Maratti- 
acese, and presumably is the case with the Ophioglossacese as 
well. In the former this is amply proven by the geological 
record; but in the others the fossil forms allied to them are 
very uncertain, and as yet poorly understood. In the Ophio- 
glossacese the series from Ophioglossum through the simpler 
species of Botrychium to the higher ones, such as B. Virgin- 
ianum, is complete and unmistakable, but when points of con- 
nection between these and other forms are sought, the matter 
is not so simple. 

Our still somewhat incomplete knowledge of the gameto- 
phyte of the Ophioglossacese makes the comparison doubly 
difficult. From the development of chlorophyll in the germi- 
nating spore of B. Virginianum, as well as from analogy with 
other Ferns, it seems probable at any rate that the subterranean 
chlorophylless prothallium is a secondary formation, but this 
cannot be asserted positively until the development is much 
better known than at present, and its relation to the green pro- 
thallium of the Marattiales and the thallus of the Hepaticse 
must remain in doubt. The structure of the sexual organs and 
development of the embryo point to a not very remote connection 
with the former order, and in some respects also to the Antho- 
cerotes. 



VIII MARATTIALES 301 

Ophioglossum beyond question shows the simplest type of 
sporangium of any of the Pteridophytes, and may be directly 
compared to a form like Anthoccros. In both cases the arche- 
sporium is hypodermal in origin, and is formed without any 
elevation of the tissue to form separate sporangia. In Antho- 
ceros, alternating with the sporogenous cells, are sterile cells 
which divide the archesporium into irregular chambers contain- 
ing the spores. A direct comparison may be drawn between 
this and the origin of the archesporium in Ophioglossum, 
especially in connection with Prof. Bower's discovery of a con- 
tinuous band of sporangiogenic tissue in the latter. In some 
species of Ophioglossum, too, the epidermis of the sporangium 
has stomata as in Anthoccros. A comparison of these remark- 
able points of similarity in the structure of the sporophyll of 
Ophioglossum and the sporogonium of Anthoccros, together 
with the very simple tissues of the former, led the writer 
(Campbell (7) ) to express the belief that Ophioglossum, of all 
living Pteridophytes, seemed to be the nearest to the Bryo- 
phytes. Subsequent study of the eusporangiate Ferns has 
strengthened that belief, and from a comparison of these with 
Ophioglossum on the one hand and the Anthocerotes on the 
other, it seems extremely likely that the latter represents more 
nearly than any other group of living plants the form from 
which the Pteridophytes have sprung, and that in the series of 
the Filicinese at any rate, Ophioglossum comes nearest to the 
ancestral type. Of course the possibility of Ophioglossum 
being a reduced form must be borne in mind, and the sapro- 
phytic habit of the prothallium may perhaps point to this ; still, 
whatever may be its real character, there is little doubt that it 
is the simplest of the Filicinese. The recent discovery of the 
interesting O. simplex strengthens this view. 

The resemblances between Ophioglossum and the Antho- 
cerotes are not confined to the sporophyte. The sexual organs 
" — and this is true of all the eusporangiate Pteridophytes — show 
some most striking similarities that are very significant. It 
will be remembered that in the Anthocerotes alone among the 
Bryophytes the sexual organs are completely submerged in the 
thallus — the antheridia being actually endogenous. It will be 
further remembered that in the eusporangiate Filicinese a 
similar condition of things exists. 



302 MOSSES AND FERNS chap. 

In all the Hepaticse the axial row of cells of the archegonuim 
terminates in the cover cell, which by cross-divisions forms the 
group of stigmatic cells of the neck. In the Anthocerotes this 
terminal group of cells is the only part of the archegonium neck 
that is free, the lateral neck cells being completely fused with 
the surrounding tissue. This arises from the archegonium 
mother cell not projecting at all, but we have seen that in cross- 
section a similar arrangement of the cells is presented to that 
found in the young archegonium of other Hepaticse. In the 
Filicineae a similar state of affairs exists, but the divisions in the 
mother cell are, as a rule, not so irregular. Still, e. g., Marattia, 
it is sometimes easy to see that the mother cell (so-called) of 
the archegonium is triangular when seen in cross-section, and 
cut out by intersecting walls in exactly the same way as the 
axial cell in the Bryophyte archegonium. In short, what is 
ordinarily called the mother cell of the archegonium in the Ferns 
is really homologous with the axial cell only of the young 
archegonium of a Liverwort. A comparison of longitudinal 
sections of the young archegonium of Marattia, for instance, 
with that of Notothylas, will show this clearly. From this it 
follows that the four-rowed neck of the Pteridophyte arche- 
gonium does not correspond to the six-rowed neck of the 
Bryophyte archegonium, but only to the group of cells formed 
from the primary cover cell, and is a further development of this. 
The relatively long neck of the archegonium in the more special- 
ised forms, e. g., Botrychium Virginianum, and especially the 
leptosporangiate Ferns, must be regarded as a secondary de- 
velopment connected probably with fertilisation. The shifting 
of the archegonium to the lower surface of the gametophyte has 
probably a similar significance. In B. Virginianum, however, 
the archegonia are borne normally upon the upper side of the 
thallus, as in the thallose Liverworts. 

It is possible that a similar relation exists between the 
antheridia of the eusporangiate Ferns and that of the Antho- 
cerotes. In both cases the formation of the antheridium begins 
by the division of a superficial cell into a cover cell and a central 
one. The former divides only by vertical walls in the Marat- 
tiacese, but in Botrychium and the Anthocerotes it becomes 
two-layered. In the latter the central cell may form a single 
antheridium, or it may produce a group of antheridia, but in 
the others it diyideg at once into a mass of sperrn cells. By the 



VIII MARATTIALES 303 

suppression of the wall in the antheridium of an Anthoceros 
where only one antheridium is formed, there would be produced 
at once an antheridium of the type found in Botrychium, and 
by a further reduction of the division of the cover cell, by which 
it remains but one cell thick, the type found in Marattia would 
result. 

Such an origin of the antheridium of the Filicinese is, at 
any rate, not inconceivable, while not so obvious perhaps as the 
resemblances in the archegonium, and is simply suggested as a 
possible solution of a very puzzling problem. 

The Marattiacese agree closely among themselves, and the 
structure of the gametophyte is like that of the Ophioglossacese, 
so far as the latter is known, and also offers most striking 
resemblances to the Hepaticse. The long duration of the pro- 
thallium, and its persistence after the sporophyte is independent, 
as well as the long dependence of the latter upon the game- 
tophyte, are all indications of the low rank of this order. The 
sporophyte, while showing many points of resemblance to the 
Ophioglossacese, still differs very much also, and in general 
habit as well as the position of the sporangia comes nearer the 
leptosporangiate Ferns. Of the Ophioglossacese, Hehnintho- 
stachys on the whole approaches nearest to the Marattiacese, so 
far as the general character of the sporophyte is concerned. 
The venation of the leaves and dehiscence of the sporangia are 
very similar to Angiopteris, and the green sterile tips to the 
sporangial branches hint at a possible beginning of the lamina 
of the sporophylls in the Marattiacese. 

The synangia of Dancca show^ a certain analogy, at least, 
with the sporangial spike of Ophioglossuni, and it is possible 
that a comparison might be made between the leaf of 0. 
palmatiim, with its numerous sporangial spikes, and a 
sporophyll of Dancoa (see Campbell (26) ). Both archegonium 
and antheridium of Ophioglossum pendulum are strikingly 
similar to those of the Marattiacese. 

While any relationship between these orders is necessarily a 
remote one, nevertheless there are too many agreements in struc- 
ture to make it at all probable that the Ophioglossacese and 
Marattiacese have had an entirely independent origin. 

In seeking a connection with the leptosporangiate Ferns 
there are two points where this is possible. The higher species 
of Botrychium show an unmistakable approach to the leptospo- 



304 MOSSES AND FERNS chap. 

rangiate type. The archegonium neck projects much more than 
in the other Eusporangiatse, and the vascular bundles in the 
petiole are truly concentric. The venation of the leaves also 
becomes that of the typical Ferns. The sporangia are com- 
pletely free and smaller and more delicate, although truly 
eusporangiate in development. In all these respects there is an 
approach to Osmunda, unquestionably the lowest of the 
leptosporangiate series. Helminthostachys too may be almost 
as well compared to Osmunda as to Angiopteris. 

On the other hand, in the circinate vernation of the leaf as 
well as the histology, in the roots and in the sporangia, the 
Marattiacese, especially Angiopteris, approach quite as close or 
closer to the Osmundacese than does Botrychium or Helmintho- 
stachys. 

We may conclude, then, from the data at our disposal, that 
the living eusporangiate Filicinese consist of a few remnants of 
widely divergent branches of a common stock, which formerly 
was predominant, but has been supplanted by more specialised 
modern types. From this primitive stock have arisen on the 
one hand the leptosporangiate Ferns, and Cycads, on the other, 
through Isoetes, or some similar heterosporous forms, the 
Angiosperms. 



CHAPTER IX 

FILICINE^ LEPTOSPORANGIAT^ 

The Leptosporangiatae bear somewhat the same relation to the 
eusporangiate Ferns that the Mosses do to the Hepaticae, but 
the disproportion in numbers is much greater in the former 
case. While the whole number of living Eusporangiatse is 
probably less than 50, the Leptosporangiatse comprise about 
4000 species. In the former the differences between the 
groups are so great that there is some question as to their near 
relationship, while all the leptosporangiate Ferns show a most 
striking similarity in their structure, and except for the presence 
of heterospory in two families, might all be placed in a single 
order. Carrying our comparison still further, we may com- 
pare the Polypodiacese, w^hich far outnumber all the others, with 
the Bryales among the Mosses. Both groups are apparently 
modern specialised types that have supplanted to a great extent 
the lower less specialised ones. 

The distribution of the leptosporangiate Ferns, too, offers 
some analogy with the Mosses. While the eusporangiate 
Ferns are few in number of species, they are for the most part 
also restricted in numbers of individuals. The Leptosporan- 
giates, on the other hand, occur in immense numbers, especially 
in the tropics, where they often form a characteristic feature of 
the vegetation. This is true to a limited extent in temperate 
regions also, where occasionally a single species of Fern, e. g., 
Pteris aquilina, covers large tracts of ground almost to the ex- 
clusion of other vegetation. A somewhat prevalent idea that 
the Ferns of to-day form merely an insignificant remnant of a 
former vegetation is hardly borne out by the facts in the case. 
Any one who has seen the wonderful profusion of Ferns in a 
20 30s 



3o6 MOSSES AND FERNS chap. 

tropical forest, and the enormous size to which many of them 
grow, is very quickly disabused of any such notion. 

The fossil record is also extremely instructive as bearing on 
this point. According to Solms-Laubach (2) there is but one 
certainly authentic case from the Carboniferous rock which can 
be regarded certainly as a leptosporangiate form, all of the 
other sporangia discovered being of the eusporangiate type. In 
the later formations the Leptosporangiates increase in number, 
but according to Luerssen ((7) II, p. 574) undoubted Poly- 
podiacese are not found before the Tertiary, where a number of 
living genera are represented. 

Potonie (3) cites several examples of Palaeozoic Ferns 
probably allied to the lower leptosporangiate families, but the 
number is very small compared to the eusporangiate types. 

Except in the few heterosporous forms there is, on the 
whole, great uniformity in the gametophyte. The most 
marked exception to this is the filamentous protonema-like pro- 
thallium of some species of Trichomanes and Schizcea. Except 
in these, however, the germinating spore, either directly or after 
forming a short filament, produces normally a flat, heart- 
shaped prothallium, growing at first by a two-sided apical cell, 
the prothallium being at first one cell thick, but later producing 
a similar cushion to that found in Marattia but less prominent, 
and the wings always remain one cell thick. Upon the lower 
side of the cushion are produced the archegonia, which have 
always a projecting neck, sometimes straight, but more com- 
monly bent backward. The antheridia are produced upon the 
same prothallium as the archegonia in most forms, but a few 
species of Ferns are dioecious, and usually there are small male 
prothallia in addition to the large hermaphrodite ones. The 
antheridia, like the archegonia, always project above the surface 
of the prothallium. 

The first divisions in the embryo always divide it into 
regular quadrants, and the young members always grow from 
a definite apical cell, which, with the possible exception of some 
of the Osmundacese, is also found at the apex of the later roots 
and always in the stem. In size the sporophyte varies ex- 
tremely. In some of the smaller Hymenophyllacese the creep- 
ing stem is not thicker than a common thread, and the fully- 
developed leaves scarcely a centimetre in length. The other 
extreme is offered by the giant tree-ferns belonging to the Cya- 



IX FILICINE^ LEPTOSPORANGIAT^ 307 

theacese, e. g., Alsophila, Cyathea, Cihotmm. The leaves are 
in most cases compound, and either firm and leathery in texture, 
or in the delicate Hymenophyllacese have the lamina reduced to 
a single layer of cells, so that in texture it recalls a moss leaf. 
With the single exception of the Salviniace?e the leaves are 
always circinate in the bud. The surface of the stem and leaves 
is frequently provided with various epidermal outgrowths, 
scales and hairs, which show a strong contrast to the mostly 
glabrous Eusporangiatse. The vascular bundles are, both in 
the stem and petioles, of the concentric type with a very distinct 
endodermis, and in the older parts of both stems and leaves 
parts of the ground tissue are often changed into thick-walled 
and dark-coloured sclerenchyma. In the finer veins of the leaf 
the vascular bundles are reduced in structure and more or less 
perfectly collateral. 

The sporangia are extremely uniform in structure through- 
out the group. They can be traced back to a single epidermal 
cell, in most cases developed from the lower side of the un- 
modified sporophylls, as in the Marattiacese. They are always 
more or less distinctly stalked, and grow for a time from a 
pyramidal apical cell, whose growth is stopped by the formation 
of a periclinal wall (Fig. 190). The central tetrahedral cell 
has first a layer of tapetal cells cut off from it, and the inner cell 
then forms the archesporium. No sterile cells are formed in 
the archesporium, but all the cells (except in the macro- 
sporangium of the Hydropterides) develop perfect spores. 
The ripe sporangium is provided, except in the Hydropterides, 
with an annulus or ring of thickened cells, which assists in its 
dehiscence, and forms the most characteristic structure of the 
ripe sporangium. 

Non-Sexual Reproduction 

In a few of the Ferns special non-sexual reproductive 
bodies, buds of different kinds, occur upon the prothallium, 
which thus may have an unlimited growth. Such buds may 
have the form of ordinary branches, or they are of a special 
form. Buds of the latter class occur, sometimes in great num- 
bers, in certain Hymenophyllacese, where they are formed upon 
the margin of the prothallium, to which they are attached by 
short unicellular pedicels from which they readily become de- 



3o8 



MOSSES AND FERNS 



CHAP, 



tached. In this way, as well as by the separation of ordinary 
branches, the prothallia of some species of Hymenophyllum 
form dense mats several inches in diameter, which look exactly 
like a delicate Liverwort. A most remarkable case is that of 
Anogramme leptophylla, examined by Goebel (i). The pro- 
thallium multiplies extensively by buds, some of which form 
tuber-like resting bodies, by which the prothallium becomes 
perennial. The sporophyte in this species is annual and dies as 
soon as the spores ripen. The archegonia are borne on special 
branches of the prothallium, which penetrate into the ground 
and lose their chlorophyll. Goebel ((lo) p. 245) suggests 



A. 




Fig. 171. — A, Prothallium of Pteris cretica, with the sporophyte, sp, arising as a veg- 
etative bud; B, apex of the root of Asplenium esculentum, developing into a leafy- 
shoot. (A, after De Bary; B, after Rostowzew.) 

what seems very probable, that the subterranean prothallium 
of the Ophioglossacese may be of this nature, and the fact that 
in Botrychinm Virginianum the germinating spore develops 
chlorophyll would point to this. 



Apogamy and Apospory 

Apogamy, or the development of the sporophyte from the 
prothallium as a vegetative bud, was first discovered by Farlow 
(i) and later investigated by De Bary (2), Leitgeb (13), and 
Sadebeck (6). It is known at present in Pteris Cretica^ As-. 



IX 



FILICINE^ LEPTOSPORANGIAT^ 



309 



pidium aiix-mas var. cristatum, Aspidhim falcatiim, Todea 
Africana, and several others. Sometimes archegonia are pro- 
duced, or they may be absent from the apogamous prothalHum, 
but antheridia usually are found. When archegonia are 
present they do not appear to be functional. In Pteris Cretica 
(Fig. 171, A), where usually no archegonia are developed, the 
cushion of tissue which ordinarily produces them is formed as 
usual ; but instead of forming archegonia it grows out into a 
leaf at whose base is formed the stem apex, w^hich soon pro- 
duces a second leaf. The first root arises endogenously near 
the base of the primary leaf, and the young plant closely resem- 
bles the sporophyte produced in the normal way. Previous to 
the development of the bud there 
is formed in the prothallium it- 
self a vascular bundle which is 
continued into the leaf, but 
is entirely absent from normal 
prothallia. 

The opposite state of affairs, 
where the gametophyte arises di- 
rectly from the sporophyte with- 
out the intervention of spores, is 
known in a number of species, 
and has been especially investi- 
gated by Bower (6). He found 

that there were two types of Fig. 172.— Pinna from the leaf of Cys- 

^ J , topteris bulbifera, with a bud ik) 

apOSpOry, as he named the ^t the base, X2; s. the sori (after 

phenomenon, one where the pro- Atkinson). 
thallium was produced from a 

sporangium arrested in its normal growth, and by active multi- 
plication of the cells of the stalk and capsule w^all forming a 
flattened structure, which soon showed all the characters of a 
normal prothallium with sexual organs. In the second case the 
prothallia grew out directly from the tips of the pinnae, and 
there was no trace of sporangia being formed previously. The 
first observations of these phenomena w^ere made upon two 
varieties, Athyrhim iilix-focmina var. clarissima and Poly- 
stichum angular e var. pulcherrinmm, but since, Farlow^ (2) has 
discovered the same phenomenon in Pteris aquilina. In the 
latter the prothallia were always transformed sporangia. The 
phenomenon of apospory was first observed by Druery ( i, 2). 



k.- 




310 MOSSES AND FERNS chap. 

The production of secondary sporophytes as adventitious 
buds upon the sporophyte is a regular occurrence in some 
species. Asplenium hiilhiferum and Cystopteris bulbifera are 
famihar examples of such sporophytic budding. In these large 
numbers of buds are formed which soon develop all the charac- 
ters of the perfect sporophyte. Very early a definite apical cell is 
established from which all the other parts are derived. In 
Camptosorus rhizophyllus, the ''walking fern" of the Eastern 
United States, a single bud is formed at the tip of the slender 
leaf which bends over until it takes root. From this terminal 
bud another leaf grows and roots in the same way. 

Classification of the Leptosporangiatce 

The Leptosporangiatse fall into two groups, which may be 
termed orders, although the two families in the second order 
(Hydropterides) are not closely related to each other, but each 
has nearer affinities with certain of the homosporous forms. 

I. Homosporous Ferns with large green prothallium, usu- 
ally in its early stages growing from a single apical cell; more 
commonly monoecious, but sometimes dioecious. Leaves always 
circinate in vernation. Sporangia with a more or less de- 
veloped annulus, either borne upon ordinary leaves or on 
specially modified sporophylls. Usually, but not always, each 
group of sporangia (sorus) covered by a special covering, the 
indusium. , 

Order I. Filices. (Eufilicinese. Sadebeck (7)). 

Family i. Osmundacese. 
Family 2. Gleicheniacese. 
Family 3. Matoniacese. 
Family 4. Hymenophyllaceae. 
Family 5. Schizseacese. 
Family 6. Cyatheacese. 
Family 7. Parkeriacese. 
Family 8. Polypodiacese. 

II. Heterosporous forms, either aquatic or amphibious ; the 
prothallia are always dioecious, the female prothallium with 
chlorophyll and capable of more or less independent growth 
when not fertilised; male prothallium always without chloro- 
phyll, the vegetative part reduced to one or two cells, besides 
the antheridium. Leaves either circinate (Marsiliacese) or 



IX FILICINE^ LEPTOSPORANGIAT^ 311 

folded (Salviniacese) ; sporangia without an annulus and borne 
in special '^sporocarps," which are either modified branches of 
ordinary leaves (Marsiliaceae) or a very highly developed 
indusinm. 

Order II. Hydropterides. 

Family i. Marsiliacese. 

Familv 2. Salviniaceae. 

» 

Order I. Filices 

The eight families of the Filices form an evidently very 
natural group, but there has been a good deal of disagreement 
as to their relative positions. The Osmundacese are generally 
recognised as approaching most nearly the eusporangiate Ferns, 
and the Gleicheniacese come next to these. The Hymeno- 
phyllaceae are usually considered at the other extreme of the 
series, but there are a number of reasons why this seems doubt- 
ful, and I am inclined to assign them an intermediate position. 
Their structure and development give evidences of their being 
a specially modified group adapted to living in very damp 
situations, and they probably cannot be regarded as connecting 
any of the other families, but rather as a side branch which has 
developed in a direction away from the type. They come near- 
est the Gleicheniacese and Osmundaceae in the structure of the 
sexual organs, and the sporangium shows points in common 
with the former family. The sporangium, however, also re- 
sembles that of the CyatheacCcX, and the strongly-developed in- 
dusium is much like that of the latter. The Schizseaceii^ also 
may possibly form a side branch from the ascending series 
which ends in the Polypodiacese. 

Professor Bower (19), who does not recognize the Ophio- 
glossacese as belonging to the Filicinese, divides the other hom- 
osporous Ferns into three suborders, based upon the develop- 
ment of the sporangia. His first suborder, "Simplices," includes 
the Marattiacese, Osmundacese, Schizgeacese, Gleicheniacese, and 
Matoniacese. In these families all the sporangia in a sorus are 
developed simultaneously, and the output of spores is rela- 
tively large. The second suborder, ^'Gradatse," comprises the 
Hymenophyllacese (inc. Loxsomaceae), Cyatheaceae (inc. Dick- 
soniese — in part), and one sub- family, Dennstaedtinese, belong- 
ing to the Polypodiaceae. In these the sporangia arise in 



312 MOSSES AND FERNS chap. 

basipetal succession on the receptacle. The remaining sub- 
families of the Polypodiacese constitute the suborder, *'Mixtai," 
in which sporangia of very different ages are mixed together in 
the same sorus. 

The well-known Ostrich-Fern, Onoclea struthiopteris 
(Struthiopteris Gernianica) illustrates very satisfactorily the 
germination of the spores and the development of the gameto- 
phyte and embryo in the Polypodiacese, the typical modern 
Ferns. 0. sensihilis, which may probably be better separated 
generically from Struthiopteris, agrees closely with the latter in 
the development of the gametophyte. 

The large oval spores contain, besides much oil and some 
starch, numerous small crowded chloroplasts. The three walls 
of the spore are plainly demonstrable, especially as the brown 
perinium is often thrown off by the swelling of the spore, and 
the transparent exospore can then be seen, with the delicate 
endospore lying close to its inner face. A large nucleus 
occupies the centre of the spore. Contrary to the statements 
usually made that spores containing chlorophyll quickly lose 
their vitality, these will germinate after a year or more, although 
not so well as those of the same season, but they normally 
remain from autumn until spring before they germinate. O. 
sensihilis acts in the same way, and spores of other Ferns con- 
taining chlorophyll have been germinated after an equally long 
period. 

The spores germinate promptly, varying from two or three 
days to about a week, depending upon the temperature. The 
exospore is ruptured irregularly near one end, and through this 
a short colourless papilla protrudes and is shut off by a trans- 
verse wall (Fig. 173, B). This papilla contains little or no 
chlorophyll and rapidly lengthens to form the first rhizoid, 
which undergoes no further divisions. The large green cell 
alone produces the prothallium. The divisions in the pro- 
thallial cell vary somewhat, but in the great majority of cases a 
series of transverse walls is first formed, and the young pro- 
thallium (Fig. 173, C) has the form of a short filament. 
Sooner or later, in normally-developed prothallia, the terminal 
cell of the row becomes divided by a longitudinal wall, which 
may be straight, but more frequently is oblique and followed 
by another similar wall in the larger of the two cells, meeting it 
so as to include a triangular cell, which is the ''two-sided" apical 



IX 



FILICINE/E LEPTOSPORANGIAT^ 



313 




Fig. 173. — Onoclea struthiopteris. A, B, Germinating spores with the perinium re- 
moved, X300; C, young prothallium, Xioo; D, E, older prothallia with two-sided 
apical cell (x), X300; F, small female prothallium seen from below, X25; G, 
very young prothallium with the two outer spore-coats, X300; r, primary rhizoid; 
ar, archegonia; p, perinium; ex, exospore. 



314 MOSSES AND FERNS chap, 

cell of the next phase of the prothallium's growth. The 
divisions up to this point correspond exactly with those of 
Aneura or Metzgeria, and are also much the same as in Mar at- 
tia, except that in Onoclea the prothallium only in very rare 
cases assumes the form of a cell mass at first. 

By the regularly alternating segments of the apical cell 
the young prothallium soon assumes a spatulate form, which 
becomes heart-shaped by the rapid growth of the outer cells of 
the young segments, which grow out beyond the apical cell. 
Sooner or later the single apical cell is replaced by two or 
more initials formed from it in the same way as in the Marat- 
tiaceae, and from this time on the growth is from a series of 
marginal initials. This change is connected with the formation 
of the thickened archegonial cushion, which, so far as I have 
observed, does not form in Onoclea so long as the single two- 
sided apical cell is present. 

As the prothallium grows new rhizoids grow out from the 
marginal and ventral cells and fasten the prothallium firmly 
to the ground. These hairs, colourless when first formed, later 
become dark brown. 

In the genus Onoclea, as well as some other Polypodiaceae, 
the prothallia are regularly dioecious, and only a part of them 
develop the archegonial meristem. The others remain one- 
layered, and are often of very irregular form, and may be 
reduced to a short row of a few cells. In Athyrium Ulix- 
fcemina these may even be reduced to a single vegetative cell 
besides the root-hair, and an antheridium. Cornu ( i ) records 
similar reduced prothallia in Aspidium Ulix-mas. All of the 
"a-meristic" prothaUia, as Prantl ((4), p. 499) calls them, are 
males. In the majority of the Polypodiaceae these occur more 
or less plentifully, and are often the result of insufficient nutri- 
tion ; but in Onoclea it is something more than this, as not only 
the small prothallia are male, but the large ones are exclusively 
female, and not hermaphrodite, as in most Ferns. 

The Sex-Organs 

The first antheridia appear within three or four weeks under 
favourable conditions, and are formed either from marginal or 
ventral cells of the prothallium. The very young antheridium 
is scarcely to be distinguished from a young rhizoid. Like it, 



IX 



FILICWEM LEPTOSPORANGIAT^ 



315 



it arises from a protrusion of the cell which is cut off by a wall, 
which is usually somewhat oblique. The papilla thus formed 
enlarges and soon becomes almost hemispherical. It contains 
a good deal of chlorophyll and a large central nucleus sur- 
rounded by dense cytoplasm. The first wall in the young an- 
theridium (Fig. 174, A) is very peculiar. It has usually the 
form of a funnel, whose upper rim is in contact with the wall of 




Fig. 174. — Onoclea struthiopteris. Development of the antheridium. A-C, Vertical 
section, X6oo; D, two nearly ripe sperm cells; E, free spermtatozoid, X about 
1200. 

the antheridium cell, and whose base strikes the basal wall of 
the antheridium. Sometimes this first wall does not reach to the 
base, in which case it is simply more or less strongly concave, 
and the basal cell cut off by it from the antheridium is discoid 
instead of ring-shaped (Fig. 174, B). The second wall is 
hemispherical, and is nearly concentric with the outer w^all of 
the antheridium. The dome-shaped central cell produces the 



3i6 MOSSES AND FERNS CHAP. 

mother cells of the spermatozoids, and has much more dense 
contents than the outer cells, but all the chloroplasts remain in 
the latter. A third wall now forms in the upper peripheral 
cell, much like the first one in form, and cuts off a cap cell at 
the top. The young antheridium at this stage consists of four 
"cells — a central dome-shaped one surrounded by three others, 
the two lower ring-shaped, and the terminal one discoid. These 
outer cells are nearly colourless and contain very little granular 
contents, except the small chloroplasts, which are mainly con- 
fined to the surface of the inner walls. 

The divisions in the central cell are at first very regular. 
The first one is always exactly vertical, and is followed by a 
transverse wall in either cell which strikes it at right angles, 
and next a third set of walls at right angles to both of these, 
so that whether seen in cross-section or longitudinal section, 
the central cells are arranged quadrant-wise. Successive bi- 
partitions follow in all the cells until the number may be a 
hundred or more, but the number is usually much less, about 
thirty-two being the commonest. The regular arrangement of 
the sperm cells soon becomes lost, and they form a mass of 
polyhedral cells with dense granular cytoplasm, and large nuclei. 
A nucleolus is visible until the last division, after which it can 
no longer be distinguished; otherwise the nuclei show no pe- 
culiarities. The transformation of the nucleus into the body of 
the spermatozoid proceeds here as in other Ferns that have been 
examined, but I was unable to satisfy myself that so large a part 
of the forward end of the spermatozoid is of cytoplasmic origin, 
as Strasburger ((ii), IV, p. 115) asserts. The fully- 
developed spermatozoid describes about three complete coils 
within the globular sperm cell, and does not lie coiled in a 
single plane, as in the Hepaticse, but in a tapering spiral (Fig. 
174, D). The very num.erous long cilia are attached at a 
point a short distance back from the apex, and as Buchtien 
((i)' P- 3^) showed, cover a limited zone, although hardly 
so restricted as he figures. 

From the investigations of Shaw (2) and Belajeff (5, 6, 7), 
it is evident that the cilia arise from a blepharoplast. Belajeff 
considers the blepharoplast in the Pteridophytes, as well as in 
the Bryophytes, to be a centrosome ; but Shaw believes that the 
blepharoplast is an organ sui generis, and of quite different 
nature from the centrosome. 



DC 



FILICINE2E LEPTOSPORANGIATyE 



317 



Mottier (3) has recently examined the structure of the sper- 
matozoid in Struthiopteris. He could detect no cytoplasmic 
envelope investing the posterior coils, which seemed to be of 
exclusively nuclear nature. The vesicle showed a fine cyto- 
plasmic reticulum in which the larger granules were imbedded. 

The separation of the sperm cells begins at about the time 
the development of the spermatozoids commences. The muci- 
laginous walls stain now very strongly, and in a living state 
appear thick and silvery-looking. The inner layer of the 
cell wall, however, remains intact, so that when the sperma- 




FlG. 175. — Onoclea struthiopteris. A, Longitudinal section of the apex of a female 
prothallium, showing the apical cell {x) and a nearly ripe archegonium, X215; 
B-D, development of the archegonium; longitudinal sections, X430; h, neck canal 
cell. 



tozoids are ejected, they are still enclosed in a delicate cell mem- 
brane, which swells up as the water is absorbed and finally 
dissolves completely. The vesicle derived from the remains 
of the cytoplasm is very conspicuous here, and the granular 
contents usually, but not always, show the starch reaction. 
The body of the free spermatozoid has the form of a flattened 
band with thickened edges, which tapers to a fine point at the 
anterior end, but is broader and blunter behind. The peripheral 
cells of the antheridium become so much compressed by the 
crowding of the sperm cells that they are scarcely perceptible. 



3i8 



MOSSES AND FERNS 



CHAP. 



but after the antheridium is burst open, the two lower ones 
become so distended that they nearly fill the central cavity. The 
opening is effected either by a central rupture of the cover cell, 
or less commonly by a separation of this from the upper ring 
cell. 

The development of the archegonium is intimately connected 
with the apical growth of the large female prothallium. As 
soon as the single apical cell has been replaced by the marginal 
initials, the divisions in the latter become very definite. Com- 
parison of cross and longitudinal sections shows that these are 

much like those of Marattia or, 
among the Hepaticse, Dendroceros 
or Pellia epiphylla. Each initial cell 
has the form of a semi-disc (Fig. 
175, A), and the growth is both 
from lateral segments, which mainly 
go to form the wings of the pro- 
thallium, and basal, or inner seg- 
ments, which produce the projecting 
archegonial cushion. If this begins 
^ to form very early, it may develop a 
midrib extending nearly the whole 
length of the prothallium ; but usually 
it does not form until relatively late. 
Each basal segment of the initial cells 
divides into a dorsal and ventral cell 
(semi-segment), the latter the larger 
of the two, and with much more 
active growth. The latter alone is 
concerned in the growth of the pro- 
jecting cushion. Each ventral semi- 
segment Is first divided by a w^all parallel with the primary 
segment wall, and from the anterior of these cells, almost 
exactly as in Notothylas, the archegonium is developed. It is 
not possible to make out any definite succession of walls by 
which the axial cell of the archegonium is cut out, but it soon 
is recognisable by the granular cytoplasm and large nucleus. 
As in Marattia, the first transverse wall separates the inner cell 
from the cap cell, and the inner one then divides into the basal 
and the central cells. The cover cell divides into the four 
primary neck cells, and the central cell arching up between these 




Fig. 176. — Ripe archegonium of 
O. struthiopteris in the act 
of opening, X300; 0, the 
egg. 



IX FILICINE^ LEPTOSPORANGIATJE 319 

has the pointed apex cut off by a curved wall from the central 
cell. The primary neck canal cell, so formed, is noticeably 
smaller than that of Marattia. The neck cells, which in the 
eusporangiate forms all grow alike, here show a difference, and 
the two anterior rows develop faster than the posterior ones, so 
that these rows are longer and the neck is strongly bent back- 
ward. In Onoclea there are usually about seven cells in each 
anterior row and about two less in the posterior ones. The 
neck cells are almost colourless, with distinct nuclei, and a few 
small, pale chloroplasts. From the central cell is now cut off 
the ventral canal cell, which is quite small, and separated from 
the egg by a strongly concave wall. The nucleus of the neck 
canal cell always divides, but no division w^all is formed, and 
the two nuclei lie free in the cell. The basal cell divides by 
cross-walls into four, and with similar cells cut off from the 
adjacent prothallial tissue constitutes the venter of the ripe 
archegonium. The disintegration of the division walls of the 
canals cells, and the partial deliquescence of the inner walls of 
the neck cells, offer no peculiarities. 

When the archegonium opens, the terminal cells diverge 
widely and the upper ones are often thrown off. 

The opening of the sexual organs and the entrance of the 
spermatozoids may be easily seen by simply allowing the plants 
to remain slightly dry for a few days until a number of sexual 
organs are mature. If these are now placed upon the slide of 
the microscope in a drop of water, in a few minutes the sexual 
organs will open, and the spermatozoids will be seen to be 
attracted to the archegonia in large numbers, and with care 
some of them may be followed into the neck and down to the 
central cell. The actual entrance of the spermatozoid into the 
egg has been observed, but is difficult to demonstrate in the 
living condition. Pfeffer (3) has shown that the substance 
which attracts the spermatozoids in the Polypodiacese is malic 
acid, and that an artificial solution of this, of the proper 
strength, will act very promptly upon the free spermatozoids of 
these Ferns. 

Buller ( I ) has found that in addition to malic acid and its 
salts, many salts, both organic and inorganic, which occur in 
the cell-sap, may exert a positive chemotactic stimulus upon the 
spermatozoids of Ferns. However, none of them react so 
strongly as malic acid and its salts. 



320 



MOSSES AND FERNS 



CHAP. 



Buller also showed that the starch which is usually present 
in the vesicle of the spermatozoid, when it escapes from the 
antheridium, disappears completely in species where the period 
of activity is prolonged. Thus in Gymnogramme Mertensii, 
the swarm-period lasted about two hours, and during this time 
the starch disappeared completely. 

Fertilisation 

Shaw (2) has made a careful study of the fertilisation in 
Struthioptcris and in Onoclea. He states that before the arche- 




--sp 




Fig. 177. — A, Osmunda cinnamomea, section of a recently fertilised archegonium, 
X4S0. A spermatozoid has penetrated the nucleus of the egg, and several are 
in the space above the egg. B, Onoclea sensibilis. Egg fourteen hours after the 
penetration of the spermatozoid, which is still recognizable within the egg nucleus, 
X900. (B, after Shaw.) 

gonium opens, the egg is depressed above, and the nucleus 
flattened. As soon as the archegonium opens, and the dis- 
organised contents of the neck cells are expelled, the tgg 
becomes turgid, and the depressed upper part forms the recep- 
tive spot. (Fig. 177.) 

The mucilaginous matter ejected from the archegonium 
retards the movements of the spermatozoids, and detaches the 
vesicle. As the spermatozoid penetrates the neck, it becomes 
much stretched out, and forces its way through to the central 
cavity of the archegonium, by a slow screw-like movement. 
Having penetrated into the ventral cavity, the coils draw 
together again, and the movements are much more rapid. 

After a spermatozoid has entered the egg at the receptive 



IX FILICINEM LEPTOSPORANGIAT^ 321 

spot, Shaw states that the egg then collapses, and suggests that 
this prevents the penetration of more than one spermatozoid. 
Mottier ((3) p. 139) expresses some doubt whether the 
collapsed appearance of the ^gg, usually found in microtome 
sections, is really normal. 

The spermatozoid soon penetrates into the nucleus of the 
^gg^ where for some time it remains with little change of form. 
Presumably the cilia and the cytoplasmic part of the sperma- 
tozoid remain in the egg-C}i:oplasm as they do in Cycas and 
Zamia ( Ikeno ( i ) , Webber ( i ) ) . 

The body of the spermatozoid, after it penetrates the egg- 
nucleus, gradually loses its homogeneous appearance, and the 
nuclear reticulum becomes more and more apparent. The 
spiral form becomes less evident, and the nucleus passes through 
much the same changes, except in reverse order, that are seen 
in its development from the nucleus of the sperm-cell. Finally 
the reticulum of the male nucleus becomes indistinguishable 
from that of the egg-nucleus, and the fusion is complete. Dur- 
ing this fusion the tgg nucleus retains its original form. 
The process of fusion is slow. In one instance, sixty 
hours after fertilisation, the sperm-nucleus was clearly recog- 
nisable. 

As soon as the tgg is fertilised it develops a membrane, 
and soon after undergoes its fir^t segmentation. The inner 
walls of the neck cells almost immediately turn dark brown, 
and the cells of the ventral part begin to divide actively and 
form the calyptra, which here, as in the Bryophytes, is formed 
from the venter alone, and is tipped with the remains of the 
neck cells. 

The position of the archegonium depends largely upon the 
light. If both sides of the prothallium are about equally 
illuminated, archegonia will develop from both sides. As soon 
as an archegonium is fertilised, no new ones form, but it fre- 
quently happens that a very large number prove abortive before 
finally fertilisation is effected. 

The Embryo 

The first division wall in all Polypodiacese yet investigated 
is vertical and nearly coincident with the axis of the arche- 
gonium. This basal wall (Fig. 178, A) at once divides the 
21 



322 



MOSSES AND FERNS 



CHAP, 



embryo into the anterior epibasal half and the posterior hypo- 
basal. The former produces the stem and cotyledon, the 
latter the primary root and foot. The early divisions are 
extremely regular, and offer a marked contrast to those in the 
eusporangiate embryo. The second wall is the transverse 
(quadrant) wall, separating the leaf and stem in the epibasal 
part, and the root and foot in the hypobasal. The next walls 
are the median or octant walls, but they do not correspond 




Fig. 178. — Onoclea sensihilis. A, two-celled embryo, X about 500; B, an eight-celled 
embryo, longitudinal section; C, two longitudinal sections of an older embryo, X 
about 250; D, E, two horizontal sections of a still older embryo; F, longitudinal 
section of an advanced embryo; the cotyledon is beginning to project beyond the 
other organs; cot, cotyledon; r, root; st, stem; /, foot. (All figures drawn from 
sections made by Dr. W. R. Shaw.) 



exactly in all the quadrants. While in the cotyledon and stem 
they are almost exactly median, in the root especially, the octant 
wall diverges often a good deal from the median line, and the 
two resulting octants are unequal in size. The following 
divisions correspond for a short time in all the octants, but 
soon show characteristic differences. For a short time each 
octant shows a definite apical growth, the segments being cut 
off by walls formed successively parallel to the three primary 



IX FILICINEJE LEPTOSPORANGIATJE 323 

divisions in the embryo, so that each octant may be said to 
have a three-sided apical cell. When the octant wall in the 
root quadrant is decidedly oblique this is not always evident in 
the smaller octant, and the larger one in this case at once 
becomes the definitive apical cell of the primary root. 

The first of these walls is usually parallel to the basal, the 
second to the quadrant wall. Sometimes this order is reversed, 
but never, apparently, is the first w^all parallel with the octant 
wall. Before the third segment is cut off from the octant, each 
of the two first ones divides by a periclinal wall into an inner 
and an outer cell. Each octant now consists of five cells, two 
inner and three outer ones, of which one is the primary octant 
cell, which still retains its original tetrahedral form. The 
outer cell of each segment divides by a radial wall, but beyond 
this the succession in the walls differs. Of the eight original 
octants, one in each quadrant persists as the apical cell respect- 
ively of cotyledon, stem, root, and foot, but in the latter it 
becomes very early obliterated by the formation of a periclinal 
wall and further longitudinal divisions, wdiich is the case also 
with one of the octants in the leaf and root. In the stem both 
octants persist, one becoming the permanent stem apex, the 
other forming the apical cell of the second leaf. 

Shaw ((2), p. 280) found in one instance an embryo in 
which the first wall in the hypobasal part of the embryo was 
the median wall instead of the usual transverse wall. 

The Cotyledon 

Of the two primary octants of the cotyledon, one very early 
ceases to grow and soon becomes indistinguishable, and the 
subsequent growth is due almost entirely to the activity of a 
single octant. The apical cell is at first like that of the other 
members, tetrahedral, but after about two sets of segments 
have been cut off from it no more are usually cut off from the 
side of the apical cell parallel to the basal w^all, and the three- 
sided cell thus passes over into a two-sided one with segments 
cut off alternately right and left. By the suppression of the 
growth in the sister octant, the apical cell gradually assumes a 
nearly median position. By the change to the two-sided form 
of the apical cell, the originally conical leaf rudiment becomes 
flattened, and a little later this is followed by a dichotomy of 



324 



MOSSES AND FERNS 



CHAP. 



the growing point and the production of -two apical cells like 
the original one (Fig. 179, C). The division is first brought 
about by a nearly central longitudinal division of the apical 
cell, and on either side of this, by a curved wall running to the 
outer wall of each cell, two new apical cells, separated by two 
elongated central cells, result. Each of these new growing 
points develops one of the lobes of the cotyledon, which undergo 
one or more bipartitions before the cotyledon breaks through 





Fig. 179. — Onoclea struthiopteris. A, Longitudinal section of young sporophyte still 
connected with the prothallium (Pr), X6o; B, the apex of same, Xi8o; C, surface 
view of the young cotyledon showing the first dichotomy; D, central region of A, 
showing the primary tracheary tissue, Xi8o; E, young sporophyte with nearly 
full-grown cotyledon and primary root, X3; st, stem; L^, cotyledon; L^ second 
leaf; F, foot; Pr, prothallium. 



the prothallium. As in Marattia the growth is much stronger 
upon the outer side and the leaf is strongly curved over. It 
very early grows beyond the stem apex, and the embryo loses its 
oval form much earlier than is the case with any of the 
Eusporangiatse. 

The Stem 

The early segmentation of the stem apex is much the same 
as in the cotyledon ; but later the divisions in the segments are 
somewhat different, and the first wall is a radial one, instead of 



^ FILICINEJE LEPTOSrORANGIATAi 325 

periclinal. The stem is very short at the time the young- 
sporophyte breaks through the prothalhum, and its apex more 
pointed than is afterwards the case. 

The Root 

At first the segmentation of the apical cell of the root is 
almost exactly like that of the stem, and it is not until several 
lateral segments, usually about two series of them, have been 
formed that the first periclinal wall, cutting off the first cell of 
the root-cap, is formed. There is a good deal of difference, 
however, as to the time this occurs, and there is probably some 
connection between it and the different period at which the 
primary root breaks through the calyptra. In most Poly- 
podiacese, the root is the first of the organs to penetrate the 
calyptra, but sometimes in Onoclca it is still short at the time 
the cotyledon is- nearly developed, and in this recalls Maraftia, 
where this is regularly the case. As soon as the first segment 
of the root-cap is formed, the segmentation of the root is 
extremely regular, and corresponds essentially to that found in 
the later roots. 

The Foot 

All definite divisions cease very soon In both of the foot 
octants, and this part of the embryo forms a more or less pro- 
jecting hemispherical mass of cells, closely appressed to the 
prothallial cells. As usual in such cases the outer cells are 
large and distinct. 

Shortly before the embryo breaks through the calyptra, 
which takes place much earlier than in Marattia, the first traces 
of the vascular bundles are seen as strands of procambium cells 
occupying the axis of each of the primary organs, and united in 
the centre, so that the four bundles together form a cross. Of 
these the one going to the foot is short, and ends blindly within 
that organ, but the others continue to grow with the elongation 
of the members to which they belong. The first permanent 
tissue to be recognised forms, as in Marattia, a bundle of short 
irregular tracheids at the junction of the young bundles (Fig. 
179, D). These primary tracheids in Onoclea are scalariform, 
but the pits are shorter than in the later ones. Throughout 
the life of the sporophyte no vessels are formed, but only 
tracheids, as in nearly all Ferns. In the cotyledon the tracheids 



326 MOSSES AND FERNS chap. 

are all spiral, and occupy the centre of the concentric bundle, 
and from these growth proceeds centrifugally. The elements 
of the phloem are poorly differentiated, and in this stage no 
true sieve-tubes could be detected. While a definite bundle- 
sheath can scarcely be made out, the limits of the bundle are 
clearly defined. The venation of the cotyledon is dichotomous, 
corresponding to the dichotomous branching of the lamina. 

The vascular cylinder of the young stem is solid, and is 
mainly composed of short and broad scalariform tracheids, but 
in the centre of the bundle are some small spiral and reticulate 
ones. The phloem at this stage is not well developed, and does 
not show perfect sieve-tubes. The bundle sends a branch to 
the second leaf, but is continued beyond the point of contact, 
and develops tracheids above the point of union before the first 
ones are formed in the leaf. In this early stage the bundle- 
sheath is very poorly differentiated in the stem, but becomes 
better marked as the plant develops. 

The primary root is monarch, and the tracheary tissue com- 
posed of short pointed tracheids with irregular scalariform 
markings. These are surrounded by one or two layers of 
narrow cells with oblique transverse septa. The calyptra is 
soon penetrated by the cotyledon, which, instead of growing 
straight up through the prothallium, as it does in Marattia, 
breaks through upon the ventral side and then bends upward 
between the lobes in front (Fig. 179, E). The root bends 
down and penetrates the earth, and very soon after, the pro- 
thallium dies. The epidermis of the cotyledon produces small 
glandular hairs, and that of the root numerous root-hairs. 

The second leaf is directly traceable to one of the primary 
stem octants, and may be either regarded as one of the primary 
members of the embryo, or as the first segment of the stem. 
Its development corresponds exactly to that of the cotyledon, 
as it does in its fully-developed state. The second root arises 
endogenously, like all the later ones, and its apical cell is formed 
close to the point of union of the bundles of the leaf and stem, 
and probably, as in the later roots, is derived from a cell of the 
endodermis. 

The new leaves arise in regular succession from the segments 
of the apical cell of the stem and up to the fifth or sixth, and 
possibly later the first division of the leaf is dichotomous, and 
the pinnate form of the later leaves is gradually attained, as in 



IX 



FILICINE^ LEPTOSPORANGIAT^ 



327 



Marattia. As the stem grows, the central stele, which at first 
is solid Cprotostelic"), becomes a hollow cylinder (''siphonos- 
tele"), which, according to Jeffrey (3) in most Polypodiaceae 
shows a concentric structure, i. c, there is a central mass of 
wood, with both outer and inner phloem, and an external and 
internal endodermis. Sometimes, however, c. g., Davallia 
stricta, both internal endodermis and phloem are absent, and 
this would seem to be the case 
also in StrntJiioptcris (Camp- 
bell (0). 

A cross-section of a plant 
of the latter species with three 
fully-developed leaves showed 
the vascular cylinder to be oval 
in outline, and consisting of the 
following parts. A central pith 
of elongated parenchymatous 
cells, surrounded by a thick ring 
of short spiral and reticulate 
tracheids, outside of which was 
a zone of phloem, the whole 
enclosed by a distinct endoder- 
mis. The latter is continuous, 
with the endodermis of the bun- 
dles going to the leaves and 
roots, and the xylem of these 
also connects with that of the 
stem bundle. The apex of the 
stem becomes more and more 
hidden by the development 

of scales from the epidermis, Fig. iSo.- Admntzimpedaiii^n. a, Rhizome 

, . , ^ ,, , 5 - . , . with young leaf. /. and the base of an 

which finally completely hide it older one: ;r, stem-apex. B. leaf-seg- 

and form a very efficient pro- ment. showing venation, and son, 5. 

tection. 

The petioles of the first three leaves have a single axial 
vascular bundle, but in the fourth, as in all subsequent ones, 
there are two. They separate very soon after leaving the stem 
bundle, which is deeply cleft where they issue from it. These 
bundles are typically concentric in structure, and have a well- 
developed endodermis. The number of roots in the young 




328 



MOSSES AND FERNS 



CHAP. 



plant exceeds the leaves. In a plant with the fourth leaf still 
unfolded, there were six fully-developed roots. 

The gaps in the vascular cylinder become more and more 
prominent as the sporophyte develops, and there is finally 
formed the wide-meshed reticulate cylinder found in the adult 
sporophyte. 

In some Ferns, e. g., Pteris aquilina, there are developed 
medullary steles which arise from the inner surface of the 
primitive stelar tube. (See Jeffrey (3), pp. 133, 134)- 




Fig. 181.— a, Vertical longitudinal section of the apex of a rhizome of Adiantum 
emarginatum, X2S; B, the central part of the same, Xi8o; L, a young leaf; C, 
cross-section of a similar stem apex, Xi8o; D, apex of a young leaf of Onoclea 
struthiopteris, showing the apical cell (jr). 



The Mature Sporophyte 



The Stem 

The stem in most of the Polypodiacese is either an erect or 
creeping rhizome which, unlike that of the Eusporangiatae, often 
branches freely. These branches are almost always formed 
monopodlally, and are usually of the same structure as the main 
axis; but in O. struthiopteris great numbers of peculiar stolons 



IX FILICINE^ LEPTOSPORANGIAT^ 329 

are formed that are quite different at first in appearance from 
the ordinary shoots. The main axis in this species is an 
upright rhizome about 2 cm. in diameter, but appearing much 
larger on account of the thick persistent leaf-bases which cover 
it. The stolons arise from the bases of these leaves, apparently 
as adventitious buds. They may remain dormant for a long 
time, as very many more of the very small ones are found than 
those that are fully developed. They finally bend upward, 
and the scattered scale-like leaves give place to the perfect green 
ones. The main rhizome is occupied by a central cylinder com- 
posed of a network of anastomosing bundles. Inside of this 
cylinder is a medulla made up of large parenchyma cells, and 
communicating with the cortex by means of the foliar gaps, or 
spaces between the bundles. 

Fig. 181, A shows a longitudinal section of the apex of a 
stem of Adiantum emarginatum, which shows the typical ap- 
pearance in the Polypodiacese. The apex of the stem forms a 
slight cone, whose centre is occupied by the large initial cell, 
which is deeper than broad. In cross-section it shows much 
the same form. Divisions occur, evidently, only at compara- 
tively long intervals, and each segment presumably gives rise to 
a leaf. The first division in each segment is longitudinal and 
perpendicular to its broad faces. Each of the six semi-segments 
is then divided into an inner and an outer cell, and the latter 
again by a longitudinal wall parallel to its inner and outer faces, 
so that each original segment is divided into two inner cells 
and four outer ones. From the inner cells the pith and vascular 
bundles arise, from the outer ones the cortex and epidermis, 
but after the first divisions there is great irregularity in the 
succession of the cells. The young vascular bundles can be 
traced nearly to the apex, and first appear as bundles of pro- 
cambium cells, which lower down unite and are joined by others 
from the leaves and roots. 

In O. struthiopteris characteristic air-chambers are formed 
in the young medulla at an early period. At certain points 
the cells become longer and their contents more transparent. 
These cells divide less rapidly than the surrounding tissue, and 
large intercellular spaces are formed. The loose cells about 
these form masses of trichomes, either hairs or scales, w^hich 
later dry up and leave a large empty space, which may or may 
not communicate with the exterior through the foliar gaps. 



330 



MOSSES AND FERNS 



CHAP. 



In Onoclea sfriithiopteriSj as in most leptosporangiate Ferns, 
the outer cortical cells become changed into sclerenchyma. 
The sclerenchyma forms several hypodermal layers, distinctly 
separated from the inner cortical parenchyma. These scler- 
enchyma cells are much elongated ; their lateral walls are some- 
what uneven, and in their younger stages swell up more 
strongly under the action of potassic hydrate than do the cortical 
cells. Their walls become thick, are first pale yellow, and later 
a dark reddish brown. The w^alls are very markedly striate, 
and the central lamella distinct. Deep pits extend down to the 
latter. 

The bundles in the stems of the Polypodiacese are very 
uniform in structure. They are usually elliptical in section, 
and the first tracheary tissue formed is a strand of small spiral . 
or reticulate tracheids at the foci of the bundle. From there 
the formation of the very large scalariform ones, so character- 
istic of the leptosporangiate Ferns, proceeds towards the centre 
of the bundle, where the last-formed ones are situated. The 
young tracheids have thin walls and abundant protoplasm, but 
as the wall thickens, the contents gradually disappear, and 



A. 





Fig. 182. — Polypodium falcatum; A, Transverse section of the rhizome, X6; B, a sin- 
gle vascular bundle, Xi7S; en, endodermis. 



finally no living protoplasm remains in them. Faint elongated 
transverse pits become evident, and the spaces between these 
rapidly thicken at the expense of the cell contents until all the 
protoplasm is used up. The thickened bars between the pits 
give the characteristic ladder-like appearance to the older 



IX 



FILICINE^ LEPTOSPORANGIAT^ 



331 



tracheid (Fig. 184, B). In cross-section these bars are nearly 
rhomboidal, and give the famihar beaded appearance to sections 
of the tracheid wall. 

Sieve-tubes of very characteristic form are found in the 
bundles of all the Polypodiaceae. In O. striithiopteris they 
occupy an irregular area at each end of the bundle. Their 
differentiation begins shortly after that of the large scalariform 
tracheids, and in some respects resembles it. The procambium 
cells from which they arise are uniform in diameter, and have 
squarer ends than the young tracheids. Their contents are 
more colourless and finely granular than those of the tracheids, 
and the nucleus not so evident. The formation of the sieve- 




en 




Fig. 183. — Woodwardia radicans. A, Part of a transverse section of a vascular bundle 
of the rhizome, X400 (about); B, transverse section of a root, X70; t, tracheids; 
s, sieve-tubes; en, endodermis. 



plates begins by transverse thickened bars on the lateral walls, 
less regular than in the tracheids, and the bars more or less 
anastomosing so as to enclose thin areas, the sieve-plates (Fig. 
184, D, E). These occur all over the lateral walls, as well as 
the transverse ones. While it could not be positively shown, it 
is extremely probable that the pores, afterwards formed, pene- 
trate completely the thin membrane of the sieve-plates, and 
throw the adjacent sieve-tubes into communication. 

While it is usually supposed that there are no nuclei in the 
adult sieve-tubes, in several instances, evidences of the presence 
of a number of small nuclei were met with. A further inves- 
tigation of this point is desirable. 

With the tracheary tissue is mingled more or less wood- 



Z2>2 



MOSSES AND FERNS 



CHAP. 



parenchyma, and in the phloem the sieve-tubes are accompanied 
by bast parenchyma. 

Outside the phloem is a layer of cells, which may be double 
in some places, and which usually contain a good deal of starch. 
According to Strasburger ( (ii), Vol. 3, p. 446) these cells do 
not constitute a true pericycle, but belong to the cortex. They 
are sister-cells of the endodermis, which is thus, not the inner- 
most cortical layer, but the next but one. The endodermal cells 
show the characteristic thickenings on their radial walls. 




par 





m 



Fig. 184. — Woodwardia radicans. A, Tracheids, t, and wood-parenchyma, par., fron? 
the rhizome, X225 (about); B, longitudinal section of two tracheids, more strong- 
ly magnified; C, section of the wall between two tracheids; D-F, sieve tubes. 



The Leaf 

While the leaf in a few of the Leptosporangiatse is simple, 
in much the larger number it is compound, either dichotomously 
branched {Adiantum pe datum) or more commonly pinnately 
divided. Owing to the great irregularity of the divisions and 
slow formation of new segments in the stem apex, it is exceed- 
ingly difficult to determine positively whether each segment of; 
the stem apex produces a leaf, but this seems probable. The 
leaf appears as a blunt conical emergence, whose apex is occu- 
pied by a single large apical cell, which in nearly all forms 
examined is wedge-shaped and forms two rows of segments. 
As the leaf grows it assumes the form of a flattened cone with a 



IX FILICINE^ LEPTOSPORANGIAT^ 333 

broad base, more convex on the outer side, and very soon show- 
ing the circinate vernation. The petiole grows much more rap- 
idly than the lamina, which remains small until the close of the 
season before which it unfolds. In most species of colder cli- 
mates the development of the leaves is very slow, and may oc- 
cupy three or four years. The last stage of growth consists 
merely in an expansion of the leaf, with comparatively little cell 
division. This latter phase of growth often goes on with great 
rapidity, in strong contrast to the excessively slow growth 
during the early stages. 

The first wall in the young segment of the apical cell 
divides it into an inner and an outer cell, and the latter then 
divides into two by a longitudinal wall, and each of the latter 
into tw^o more by a transverse wall. Of these five cells, the 
inner ones, in the lamina of the leaf, produce the rachis, the 
outer ones the lamina itself. The outer cells of the segments 
form the pinnae. Soon after the separation into lamina and 
petiole, the development of pinnae begins in those Ferns which, 
Hke O. struthioptcris, have pinnate leaves (Fig. i8i, D). Their 
formation is strictly monopodial, and begins by an increase in 
growth in the outer cells of the young segment, which thus 
forms a lobe. The marginal cells divide rapidly by longitudinal 
walls, so that at first the young pinna does not grow from a 
single apical cell, but sometimes two of the division walls inter- 
sect and an apical cell is formed. Whether this always happens 
could not be absolutely determined. As each pinna corresponds 
to a segment of the apical cell of the leaf, it follows that they 
alternate with each other on opposite sides of the rachis. 
Where they grow from an apical cell, the divisions follow 
those in the apex of the leaf. From the inner cells of the 
segments the rachis of the pinna is developed. The midrib of 
each lobe of the pinna bears the same relation to it that the 
rachis does to the pinna itself. The secondary veins arise in 
acropetal succession, and at first form a strand of procambium 
reaching from the midrib to the margin. Where dichotomy of 
the veins occurs, as it so frequently does in their ends, this is 
connected with a dichotomy of the marginal group of meriste- 
matic cells (Sadebeck (6), p. 270). Each marginal cell, like 
the segment of the apical cell of the leaf, divides into an inner 
and an outer cell. The latter then divides longitudinally, and 
the dichotomy is thus inaugurated. These secondary marginal 



334 



MOSSES AND FERNS 



CHAP. 



cells now repeat the same divisions, and the two diverging rows 
of inner cells form the beginning of the young veins. 

Except the smallest veins, which are collateral, the bundles 
are typically concentric, and differ only in minor particulars 
from those of the stem. The ground tissue of the petiole shows 
much the same structure as that of the rhizome in most Ferns, 
and usually develops several layers of hypodermal sclerenchyma. 
In the lamina, the cells of the ground tissue, or mesophyll, as the 
leaf expands, separate and form large intercellular spaces be- 




FiG. 185. — Adiantum emarginatuni. Development of the stomata, X525; v, accessory 

cell; st, stoma mother cell. 



tween them. The cells are in many places connected by pro- 
longations or protrusions of the wall. On the upper side, in 
cases where no stomata are developed, an imperfect palisade 
parenchyma may form, but in none of the forms examined by 
me was it nearly so distinct as in Angiopteris. The fully-de- 
veloped epidermal cells are very sinuous in outline, and always 
contain numerous chloroplasts. 

In Onoclea struthiopteris stomata are developed only upon 
the lower side of the lamina, but sometimes these also are found 



IX FILICINEJE LEPTOSPORANGIATJE 335 

Upon the upper surface. Usually, but not always, the devel- 
opment of the young stoma is preceded by the formation of a 
preliminary cell (Fig. 185, v), horse-shoe shaped, and cut- 
ting off a small cell from one corner of an epidermal cell. A 
similar wall forms within this small cell, parallel to the first 
one (Fig. 185, B, st), and the cell thus separated is the stoma 
mother cell. A longitudinal wall next divides this, and then 
splits in the middle to form the pore of the stoma (Fig. 185, 
C). This when complete is exactly in structure like those of 
other vascular plants, and like them communicates with the air- 
spaces of the mesophyll. The accessory cell enlarges very 
much with the expansion of the leaf, and its walls have the same 
sinuous outline that the other epidermal cells exhibit. A curi- 
ous variation of the ordinary form is seen in Aneimia (De 
Bary (3), p. 42), where the mother cell of the stoma is cut out 
by a perfectly circular wall, very much like the funnel-shaped 
one in the antheridium, and the stoma is apparently free in 
the centre of an epidermal cell. It seems that this also occurs 
in Poly podium lingua (De Bary, 1. c). 

Most of the Leptosporangiatse are characterised by numer- 
ous epidermal outgrowths, either hairs or scales. These are 
especially abundant upon the younger parts, and are largely 
protective. The hairs are either simple or glandular ones. In 
the latter case the gland is usually a terminal, pear-shaped cell, 
which secretes mucilaginous matter, or less frequently (Onoclea 
stnithiopteris) this secretion may be resinous. In the common 
Californian *'gold-back" Fern, Gymnogramme triangularis, the 
yellow powder upon the back of the leaf is a waxy secretion, 
derived from epidermal hairs. Of similar nature are the large 
chaffy scales (palese) w^hich occur in such numbers upon the 
bases of the petioles of so many Ferns. This development of 
hairs, however, is most marked in the large tree-Ferns, Dick- 
sonia, Cihotiimi, etc., where the young leaves are completely 
buried in a thick mass of brown wool-like hairs, which are 
sometimes utilised as a substitute for wool in stuffing mat- 
tresses, etc. 

The Root 

The roots arise in large numbers in most Ferns, and appar- 
ently bear no definite relation to the leaves. The primary ones 
are first visible very near the apex of the stem (Fig. 181, A, r). 



336 



MOSSES AND FERNS 



CHAP. 



and Van Tieghem ( 5 ) , who has made a very exhaustive study 
of the subject, states that they always arise from an endodermal 
cell. This divides into a basal cell and a terminal one, and by 
the former the y6ung root is dir.ectly connected with the xylem 
of the stem bundle. In the outer cell the three walls defining 
the pyramidal apical cell now arise, and the latter at once be- 
gins its characteristic divisions. 

The segmentation in the apex of the roots of the Lepto- 

sporangiatae is exceedingly regular. 
Corresponding to each set of lateral 
segments an outer segment forms 
as well. Van Tieghem does not 
apparently recognise the root-cap 
as distinct from the epidermis, but 
all other observers consider the root- 
cap as a distinct structure. The 
first division wall in the lateral seg- 
ments is the sextant wall, which is 
perpendicular to the broad faces of 
the segment and curves somewhat 
so as to strike one of the lateral 
walls a little above the base, and 
thus makes the two sextant cells of 
unequal size (Fig. 188, C). The 
next wall is transverse and sepa- 
rates an inner from an outer cell, 
and with this divides the plerome or 
stele from the cortex. After this 
in the outer of the primary cells 
there is a separation of an outer 
from an inner cell, the former giving rise either directly or by a 
subsequent division to a single layer of cells upon the outside 
of the root, which is usually regarded as the epidermis, and the 
inner cells from the cortex. The inner layer of the cortex, 
which can be traced back almost to the summit, is the endo- 
dermis. 

According to Strasburger (10) in Pteris Cretica the cap 
cells divide only by perpendicular walls, and the older layers of 
the cap remain but one cell in thickness. Van Tieghem states 
((5) J P- 53-) ^rid I have verified this in Adiantum emargina' 
turn and Polypodhim falcatiinij that with the exception of the 




Fig. 186. — Scale from the stipe of 
Cystopteris fragilis, X25. 



IX 



FILICINE^ LEPTOSPORANGIATJE 



337 



eu 



first-formed cap cell (or ''epidermal segment," to use his termin- 
ology), there is, in the central part, always a doubling of the 
cells by periclinal walls, so that each layer of the older root-cap 
is normally double, except sometimes at the extreme t(\gt. 

There is very little displacement of the cells for a long time, 
and cross-sections of the root, made some distance l^elow the 
summit, still show the limits of the original sextant walls, which 
form six radiating lines wnth periclinal walls arranged with 
great regularity. In the centre the divisions proceed with great 
rapidity, and the plerome soon shows the elongated narrow pro- 
cambium cells. In the centre are four much larger cells, which 
develop later into tracheids, and three of these can be traced 
back to the central cells 
of the three larger sex- 
tants (Fig. 1 88, D); the 
fourth arises from the in- 
ner cell of one of the smal- 
ler ones. This central 
group of cells marks the 
position of the plate of 
tracheary tissue, found 
later in the root. By this 
time the parts of the com- 
plete root are all indicated. 
The bundle is bounded 
externally by the endo- 
dermis, whose cells are 
much elongated trans- 
versely, and clearly dis- 
tinguishable from the peri- 
cambium (pericycle), which consists of one or two rows of 
cells. Inside this is the mass of procambium cells, the large 
tracheids of the central part of the xylem being very evident 
(Fig. 1 88, E). The masses of procambial cells on either side 
of this central line of cells constitute the young phloem. 

The primary tracheids (protoxylem) arise simultaneously 
at the foci of the section, and consist of a single line of narrow 
pointed tracheids, with fine spiral markings, very closely set at 
first, but later pulled apart somew^hat wnth the increase in length 
of the root. These are formed a long time before any other 
permanent tissue elements can be distinguished. Around these 




Fig. 187. — Pteris cretica. Origin of lateral 
rootlet from the endodermis of the root; en, 
endodermis of the main root; x, apical cell 
of the rootlet; p, "digestive pouch." (After 
Van Tieghem.) 



22 



338 



MOSSES AND FERNS 



CHAP. 



primary tracheids are formed a group of similar ones, and from 
here the formation proceeds towards the central group of large 
tracheids, which are the last to have their walls thickened and 
lignified. The large secondary tracheids are scalariform, like 
those of the stem. The cells of the pericycle remain nearly 
unchanged, but in the two phloem masses, according to Poir- 
ault (i) sieve-tubes are always present. These tubes are of 
two types, those with horizontal transverse walls, and those 
with inclined ones. The perforations in the sieve-plates were 




Fig. i88. — Adiantum emarginatum. A, Longitudinal; B-E, a series of transverse sec- 
tions of the root, X200; x, apical cell; s-s, sextant walls; en, endodermis. 

demonstrated, and lateral perforations, either isolated or in 
groups, also occur. His statement that the sieve-tubes have no 
nuclei requires further proof. The walls of the sieve-tubes are 
of cellulose, but in the sieve-plates callus is found. The rest of 
the phloem is composed of conducting cells, with thin walls and 
oblique septa. The endodermis often becomes dark-coloured 
and its walls lignified, and when the root dries the vascular 
cyhnder becomes separated from the ground tissue by the trans- 
verse splitting of the endodermal cells. 



IX FILICINEAi LEPTOSPORANGIAT^ 339 

The secondary roots arise in regular succession in two lines, 
corresponding to the ends of the xylem plate in the diarch 
bundle. They themselves generally branch further, and thus 
very extensive root systems are formed. The origin of the 
lateral roots of the Ferns has been exhaustively studied by 
Lachmann (7), but their position seems to be of very little im- 
portance systematically, and except in a few cases like 
Osnninda, wdiere two roots regularly arise from each leaf, there 
is little relation between roots and leaves. In creeping rhi- 
zomes they arise either mainly from the ventral side or from 
all parts indifferently. As yet the only forms in which com- 
plete absence of roots is knowai among the Leptosporangiatse 
are Salvinia, species of Trichomancs, and Stromatoptcris 
(Poirault (2), p. 147), one of the Gleicheniacese. In all of 
these, however, there are substitutes either in the form of modi- 
fied leaves {Salvinia) or root-like rhizomes. 

The formation of buds from the roots, such as occur in 
Ophioglossum, has been also observed in some Leptosporan- 
giatse. This was first discovered by Sachs in Platyccrium 
Wallichii, and later described by Rostowzew ( i ) ; and Lach- 
mann (7) also descril^es it in Anisogonium Sermaniporense. 
In all these cases the apex of the root appears to become trans- 
formed directly into the apex of the bud (Fig. 171, B). 



The Sporangium 

The development of the sporangium of all the Leptosporan- 
giatae is much the same, but the position of the sporangia, and 
the character of the indusium when present, vary much, and 
will be discussed later as the different families are treated sep- 
arately. 

In the Polypodiacese the sporangia, as is well knowm, arise 
usually in groups (sori) upon the backs of leaves that differ 
but little from the ordinary ones. Sometimes, however, e. g., 
Onoclea, they are very different, the sporangia being produced 
in great numbers, and the lamina of the leaf is much contracted. 
One of the simplest cases is seen in Polypodiiim. Here the 
sporangia develop late upon ordinary leaves, and form scat- 
tered round sori, bearing, however, a definite relation to the 
veins — in this case forming above the free end of one of the 



340 



MOSSES AND FERNS 



CHAP. 



small veins. Where there are special sporophylls, the develop- 
ment of the sporangia begins before the leaves begin to unfold. 
In Poly podium (Fig. 190) the first evidence of the forma- 
tion of sporangia is a series of minute depressions upon the 
lower side of the leaf, much as occurs in Angiopteris. The 
bottom of this depression is occupied by a low elevation, the 
placenta, and upon this the sporangia form in an analogous 




St. 



B. 




Fig. 189. — Polypodium falcatutn. A, Cross-section of a sterile leaf, cutting across one 
of the smaller veins, X260; st, section of a stoma; B, similar section of a sporo- 
phyll, showing the position of the sorus above the vein, X85. 



way, but are not all developed at the same time, so that a single 
sorus may contain nearly all stages of development. The spo- 
rangium here can be readily traced back to a single epidermal 
cell. 

The sporangial cell protrudes until it is nearly hemispher- 
ical, when it is cut off by a wall level with the surface of the 



s 



IX 



FILICINEAl LEPTOSPORANGIATjE 



341 



placenta. The basal cell takes no further part in the develop- 
ment of the sporangium, and after a time becomes indistin- 
guishable. The outer cell now divides by a wall, occasionally 
transverse, but much more commonly strongly inclined (Fig. 
190, A), and striking the basal wall. This is now followed by 
two others, also inclined, and meeting so as to enclose a pyram- 
idal apical cell, from which a varying number of lateral seg- 
ments are cut off. These form three rows, corresponding to 
the three rows of cells found in the stalk, which is not sharply 
separated from the capsule, as stated by GoeM ((10), p. 218), 
and formed from the lower of two primary cells, but is merged 





G. 




Fig. 190. — Polypodium falcatum. Development of the sporangium. A-E, from living 
specimens; F, G, microtome sections; A, B, C, optical sections; D, E, the same 
* sporangium, showing respectively the surface cells and central optical section; t, t, 
tapetum. A-E, X400; F, G, X200. 



gradually into the capsule, and owes its three-rowed form to a 
primary and not a secondary division. The upper part of the 
young sporangium enlarges, so that it becomes pear-shaped 
(Fig. 190, B), and a periclinal wall is then formed in the apical 
cell. The cells of the stalk undergo no longitudinal divisions, 
and it remains permanently composed of three rows. 

Kiindig ( i ) first called attention to the real state of affairs, 
and since, C. Miiller (2) has investigated the matter further. 



342 MOSSES AND FERNS chap. 

The central tetrahedral cell of the young sporangium (arche- 
sporium) has cut off from it, by periclinal walls, the primary 
tapetal cells (t), and in the meantime the wall of the capsule 
forms repeated radial divisions but no periclinal ones, and, un- 
like that of the eusporangiate Ferns, always remains single- 
layered. A surface view of the sporangium at this stage shows 
the last-formed lateral segment to still retain its triangular 
form, and the cell divisions in it are very regular. After two 
or three transverse divisions, a median vertical wall follows, 
and in each of the resulting cells a transverse wall. Of the two 
upper cells, one, according to Miiller, remains undivided, the 
other divides again by a vertical wall, and the inner of the two 
cells thus formed by further transverse divisions forms the 
stomium or mouth of the sporangium. 

The cells of the young sporangium contain but little gran- 
ular contents, and the divisions are very evident. As soon 
as the archesporium is formed its contents begin to assume a 
more granular appearance, and become more highly refractive 
than those of the surrounding cells. The contrast between the 
archesporial cells and those of the wall increases as the sporan- 
gium grows older. 

The first division in the central cell begins soon after the 
separation of the primary tapetal cells. The direction of this 
first wall is usually transverse, but may be more or less inclined, 
or even vertical. In each of these cells a wall is formed at 
right angles to the first-formed, and the quadrant cells are 
again divided into equal octants. Each of these eight cells 
divides once more (Fig. 190, G), and the sixteen spore mother 
cells, found in most Ferns, are complete. In Onoclea struthi- 
opteris I found twelve as the ordinary number, but at what 
point the division is suppressed was not made out. During the 
division of the central cells the tapetal cells also divide, first by 
radial walls only, but later by one set of periclinal walls. This 
doubling of the tapetum, while it occurs in the majority of 
Polypodiacese, does not seem to be universal (Goebel (10), 
p. 218) . The cells of both sporogenous cells and tapetum have 
dense granular cytoplasm, and large nuclei. Soon after the 
divisions in the sporogenous complex are completed, the walls 
of the tapetal cells become broken down, and their contents 
dispersed through the large central cavity. The sporangium 
continues to enlarge rapidly after this, and the spore mother 



IX riLICINE^ LEPTOSPORANGIATAE 343 

cells, still united, lloat in a lar^^e cavity, whicli in the living 
sporangium seems to be filled with a structureless mucilaginous 
fluid, but when fixed and stained is seen to contain the un- 
changed nuclei of the tapetum, as well as its cytoplasmic con- 
tents. Gradually the connection between the sporogenous cells 
is lost, and the isolated cells, each surrounded Ijy a very delicate 
membrane, float in the large central cavity. Here they divide 
into four cells, as usual, and the division may be simultaneous, 
resulting in tetrahedral spores, or successive (Onoclea), in 
which case bilateral spores are formed. Strasburger ((12), 
p. 239) states that during the division of the spores in Osmimda 
there is a reduction of the chromosomes to one-half their orig- 
inal number, but in a later paper (14) he reports that although 
there is a reduction in the number of chromosomes, the ratio of 
tw^elve to twenty-four, which was first given, is not absolutely 
constant. Stained microtome sections of sporangia during the 
formation of the spores show that the spore mother cells, and 
afterwards the spores themselves, are embedded in a granular 
matter, evidently the product of the disorganised tapetum, and 
that the nuclei of the latter are collected about them, evidently 
intimately associated w^ith the growth of the young spores, and 
in the later stages, with the formation of the perinium. The 
latter is rarely smooth, but shows spines, ridges, and folds of 
characteristic form in different species. 

When chlorophyll is present in the ripe spore it only arises 
at a late period. In Onoclea striithiopteris, about the time that 
the perinium begins to form, numerous small colourless gran- 
ules appear near the nucleus, and \vith the ripening of the spore 
these increase rapidly in size and number, and an examination 
show^s that the increase in number is the result of division. 
These are young plastids, and as they enlarge, chlorophyll is 
formed in them and they become very much crowded, so that 
the green colour of the ripe spore is very pronounced. 

The further history of the sporangium wall is somewhat 
complicated. The stomium, as we have seen, arises from a 
special cell of the last-formed lateral segment. The segment 
on the opposite side (next older but one) shows a quite similar 
arrangement of cells, and, according to IMiiller, the cell corre- 
sponding to the stomium by two transverse walls forms the 
first segment of the annulus. The cells immediately below also 
divide similarly, and give rise to a second section. The rest of 



344 



MOSSES AND FERNS 



CHAP. 



the annulus arises from the upper or cap segment of the spo- 
rangium wall, and extends from the stomium over the top of 
the sporangium, and joins the part of the annulus upon the 
other side. The walls of all the cells are at first alike, but those 
of the annulus begin to thicken, this being confined to their 
inner and radial walls, the outer walls remaining thin. In most 
species the cells of the annulus are the same for the whole ex- 
tent, but in Polypodium falcatum (Fig. 191), which is figured 
here, the cells of the annulus immediately above the stomium 

are larger and thinner- 
walled. The stomium 
cells are more extended 
laterally than the other 
cells of the annulus, and 
between them the spo- 
rangium opens by a wide 
horizontal cleft 

Atkinson ((3), p. 68) 
describes the process 
o| thus for the Polypodi- 
aceae. "While the open- 
ing of the stomium be- 
tween the lip cells is aid- 
ed by their peculiar form, 
it seems possible that at 
maturity the line of un- 
ion is less firm than be- 
tween the other cells. 
The fissure once started 
proceeds across the lat- 
eral walls of the sporan- 
g i u m , usually in a 
straight line, thus split- 
ting in half the cells of the middle row, their frailty favouring 
this. The drying of the annulus brings about the unequal ten- 
sion of its cell walls. During this process it slowly straight- 
ens, carrying between the distal portion of the lateral walls 
of the sporangium, which remain attached to the free extrem- 
ity, the greater part of the spores. When straight, it continues 
to evert, and this usually proceeds until the two ends of the 
annulus nearly or quite meet, when with a sudden snap it 




Fig. 191. — Surface view of a nearly ripe sporan- 
gium of Polypodium falcatum, Xi75; st, 
stomium; r, annulus. 



IX FILICINEJE LEPTOSPORANGIATAl 345 

throws the spores violently away and returns to nearly its 
normal position." 

Paraphyses, in the form of pointed hairs, often with a 
glandular terminal cell, sometimes occur with the sporangia. 
These in some Ferns, e. g., Aspidiuin filiv-mas, are direct 
outgrowths of the sporangium itself. 



CHAPTER X 

THE HOMOSPOROUS LEPTOSPORANGIAT^ (FILICES) 

Fam. I. OsMUNDACE^ (Diels (/)) 

The Osmundacese, which in many respects form a transition 
from the eusporangiate to the leptosporangiate Fihcineae, are 
represented by two genera, Todea (inc. Leptopteris) , with four 
species, mostly confined to Australasia, one species only 
being found in South Africa; Osmunda, with six or seven 
species, belonging mainly to the temperate and warm temper- 
ate regions of the northern hemisphere. The widely distrib- 
uted species 0. regalis is found also in South Africa, but other- 
wise they belong exclusively to the northern hemisphere. Os- 
munda has the large sporangia borne on very much modified 
sporophylls, which recall strongly those of Botrychium or Hel- 
minthostachys; Todea, while its sporangia are like those of 
Osmunda, has them borne upon the backs of ordinary leaves. 

The Gametophyte 

The development of the gametophyte is completely known 
in Osmunda (Kny (5); Campbell (12)) and somewhat less 
perfectly in Todea (Luerssen (3)), which does not, however, 
seem to differ essentially from Osmunda. In the latter there 
is considerable difference in the species examined. In all of 
them the spores contain chlorophyll at maturity, and quickly 
lose their power of germination. Sown as soon as ripe, they 
germinate very promptly, and the first division of the spore 
often takes place within twenty-four hours. The early stages 
show great variation, even in the same species, and these seem 
to be often quite independent of external conditions. The un- 

346 



THE HOMOSPOROUS LEPTOSPORANGIAT^ 



34; 



germinated spore has an exceedingly delicate endospore, which 
is difficult to demonstrate, but after the exospore bursts along 
the three ventral ridges, and the endospore is exposed, it be- 
comes very evident. 

The first division takes place after the spore has elongated 
slightly, and is usually transverse, separating the small rhizoid 





^^P D 







Fig. 191. — Osmunda Claytoniana. A, Ungerminated spore; i, ventral surface; 2, 
optical section, X550; B, germinating spores, X275; r, primary rhizoid; C-E, older 
stages, X275; sp, spore membrane; x, apical cell. 



from the large prothallial cell (Fig. 191, B). The young rhi- 
zoid contains chlorophyll, but not so much as the larger cell. 
As germination proceeds the chloroplasts separate and increase 
in size. They are often arranged in lines extending from the 
large nucleus to the periphery of the cell. As a general thing, 



348 



MOSSES AND FERNS 



CHAP. 



the growth of the prothalhum is exactly opposite to that of 
the first rhizoid (bi-polar germination), and Kny ((5), p. 12) 
lays a good deal of stress upon this, as distinguishing Osmunda 
from the Polypodiacese ; but it is not at all uncommon for O. 
Claytoniana, especially, to have the axis of growth of the rhi- 
zoid almost or quite at right angles to that of the prothallium, 
exactly as in the Polypodiacese. Where the germination is 
truly bi-polar the exospore is pushed up with the growing pro- 
thallium, and appears like a cap at its apex, but if the rhizoid is 
lateral, the exospore remains at the base. 

In 0. Claytoniana there are usually several transverse walls 
A, 



B. 





Fig. 192. — Osmunda cinnamomea. A, Young prothallia; B, an older prothallium, X260. 



formed before any longitudinal ones, but in O. cinnamomea 
and O. regalis it is quite common to have the first transverse 
wall followed by a longitudinal wall in each cell, so that the 
four primary cells are arranged quadrant-wise (Fig. 192, A, 
c). Rarely the first wall in the prothallial cell is longitudinal, 
as is often the case in Equisetum, and sometimes the first divi- 
sions are in three planes, so that a cell mass is formed at once, 
as so often occurs in the Marattiacese. Where a filamentous 
protonema is formed, a two-sided apical cell is soon established 
in exactly the same way as in Onoclea. Where the four quad- 
rant cells are formed, one of the terminal ones becomes at once 
the apical cell. - 



X THE HOMOSPOROUS LEPTOSPORANGIATAi 349 

As soon as the apical cell is established, j^rowth proceeds 
as in Onoclea, and a heart-shaped prothallium is formed. One 
difference, however, may be noted. Each segment cut off from 
the apical cell divides first by a transverse wall into an inner 
and an outer cell, but the inner cell from the first undergoes 
divisions by horizontal walls, so that a central midrib is formed, 
very much as in Mctzgeria, and the prothallium becomes more 
elongated than is common in the Polypodiaceae. The single 
two-sided apical cell persists for a long time, but is finally 
replaced either by a single cell, much like that of Pcllia 
epiphylla, or more commonly by a series of marginal cells, as 
in the Marattiacese or Polypodiacese. The subsequent growth 
of the prothallium is the same as in those forms, but no definite 
relation could be made out between the archegonia and the 
segments of the initial cells. Among the Hepaticae Dendro- 
ceros offers almost an exact analogy in the form of the apical 
cells and the divisions of the segments. 

According to Luerssen (3), in Todea a distinct apical cell 
is often wanting, and the growth throughout is due to the 
activity of several similar initials. His figures, however, 
hardly bear out his statement, and further information is de- 
sirable on this point. 

As the prothallia grow older the midrib becomes conspicu- 
ous, and projects strongly from the ventral surface. In O. 
cinnamomea and 0. regalis even at maturity it is very little 
broader where the archegonia are formed; but in O. Claytoni- 
ana it forms a cushion in front, much like that of Maraftia or 
the Polypodiacese, and in this respect, as well as in the form of 
the apical cells, seems to approach the latter. In this species 
the prothallium is lighter coloured, and the rhizoids not so 
dark, wdiile in its dark green colour and fleshy texture 0. cin- 
namomea recalls Anfhoceros Iccvis or Marattia. 

Where a cell mass is formed at first, this condition is tem- 
porary, and an apical cell is established which gives rise to the 
ordinary flat prothallium. The small male prothallia, which are 
produced in large numbers, exhibit various irregularities and 
quite commonly do not show any definite apical growth, and in 
O. Claytoniana especially often branch irregularly, or in some 
cases there is a true dichotomy (Fig. 193, A.) Slender fila- 
mentous prothallia are especially common in this species (Fig. 
194, C), and recall somewhat those of some species of Trich- 
omanes. 



350 



MOSSES AND FERNS 



CHAP. 



The prothallia of the Osmundacese often form adventitious 
buds, much Hke those of the Marattiacese. These secondary 
prothalha (Fig. 194, B) generally arise from the margin, but 
may be produced from the ventral surface. An apical cell is 
usually early established, and the subsequent growth is closely 
like that of the primary one. 

A. 




Fig. 193. — A, Apex of a young prothallium of O. Ctaytoniana, with two similar initials, 
X, X, X560; B, longitudinal section of an advanced prothallium of O. cinnamomea, 
X260; C, horizontal section of a similar one, showing two initials, X260. 

The prothallia are long lived if they remain unfertilised, 
and Goebel ((i6), p. 199) states that in O. regalis they may 
reach a length of four centimetres. He also records a genuine 
dichotomy of the older prothallia of this species. 



The Antheridium 



f 



Under favourable circumstances the first antheridia appear 
after about a month in O. Claytotiiana, and continue to form 



THE HOMOSPOROUS LEPTOSPORANGIATAi 



351 



for a year or more. In O. cinnamomea they first appeared 
about two weeks later. While they are almost always present 
upon the large female prothallia/ numerous exclusively male 
plants are always met with. These latter are usually irregular 
in form, and even filamentous, especially when crowded. Upon 
the latter the antheridia are either terminal or marginal ; in the 
flattened prothallia they occur mainly upon the margin and 




Fig. 194. — A, Prothallium of O. Claytoniana, about two months old, X about 30; B, 
base of an older prothallium of the same species with a secondary prothallium 
ipr^) growing from it, X8o; ^, antheridia; C, small branching male prothallium 
of the same species, X7S. 



lower surface of the wrings. The development corresponds 
closely in all forms that have been examined, and differs con- 
siderably from that of the Polypodiace^e. 

The mother cell is cut off as usual, but the second wall is 
not funnel-shaped, but plane and inclined, so that it strikes the 
basal cell. In the larger of the two cells thus formed a vary- 

* Luerssen (/. c. p. 449) states that they are often absent from very vig- 
orous prothallia.^ 



352 



MOSSES AND FERNS 



CHAP. 



ing number of divisions occur, cutting off a series of lateral 
segments, much after the fashion of a three-sided apical cell. 
The segments thus cut off form the basal part of the anther- 
idium, and when the number is large a pedicel may be formed. 
When the full number of basal segments is complete, a dome- 
shaped wall arises in the apical cell, as in the Polypodiacese, and 
the central cell has much the same form (Fig. 195, A). This 
has no chlorophyll, and as usual the large distinct nucleus is 
embedded in dense highly refractive cytoplasm. There are 






Fig. 195. — A-D, Development of the antheridium of O. cinnamomea, in longitudinal 
section, X42S; E, F, G, three surface views of ripe antheridia of O. Clay- 
toniana; E, from above, the others from the siOe; 0, opercular cell, X425. 



next developed in the outer dome-shaped cell two or three walls, 
running more or less obliquely over the apex ; either at the top 
or at one side the last-formed wall encloses a small cell, which 
is thrown off when the antheridium opens (Fig. 195, o). This 
opercular cell, both in form and position, recalls strongly that 
found in the Marattiaceas. 

The divisions in the central cell -correspond closely to those 
in Onoclea, but the number of sperm cells is larger, being usu- 
ally 100 or more. The development is also the same, and will 
not be entered into here.^ After the final division of the sperm 
cells the nuclei remain slightly flattened in the plane of division, 

^ For details see Campbell (12), p. 61, 



THE HOMOSPOROUS LEPTOSPORANGIATjE 



353 



as in the Hepaticae, and the mature spermatozoids are coiled 
more flatly than in the Polypodiacea^. The free spermatozoid 
recalls that of Marattia or Equisctum rather than that of the 
Polypodiace^e. There are but about two complete coils, and 
the hinder one relatively larger than in the latter forms. In 
swimming there is peculiar undulating movement, suggestive 
of the spermatozoid of Equisctum. 

The Archegonium 
The archegonia are only borne upon the large heart-shaped 




Q-. 



Uo 





Fig. 196. — A, Ripe antheridium of O. Claytoniana, just ready to open; B, the same 
discharging the sperm cells, X600; C, two spermatozoids, X1200; o, operculum. 



prothalHa, and occupy the sides of the projecting midrib, where, 
if the earlier ones are not fertilised, they may continue to form 
indefinitely ; but no correspondence can be made out between 
them and the initial cells, and while developed for the most part 
in acropetal order, new ones may arise among the older ones. 
23 



354 



MOSSES AND FERNS 



CHAP. 




B 



The mother cell of the archegonium is scarcely distinguishable 
from the neighbouring cells, either in size or contents, and can- 
not always be identified until after the first transverse divisions. 
The development is much as in the other Ferns, but there are 

some differences that may 
be noted. The first trans- 
verse division, as in these, 
separates the cover cell from 
the inner cell, and the latter 
may divide into a basal and 
central cell, but sometimes 
this division is omitted, and 
the basal cell is absent. The 
cover cell divides by the usual 
cross - walls into the four 
primary neck cells, which 
here all develop alike, and the 
neck remains straight. The 
complete neck has about six 
tiers of cells. The separation 
of the neck and ventral canal 
cells follows in the usual 
manner, but occasionally the 
former may be divided by a 
transverse cell wall (Fig. 
197, A), although ordinarily 
the division is confined to the 
nucleus. The neck cells have 
small nuclei, and in the liv- 
ing state are almost trans- 
parent, with little chloro- 
phyll. Small glistening bod- 
ies, apparently of albumin- 
ous nature, are often present, 
and are especially conspicu- 
ous in material fixed with 
chromic acid. Kny and 
Luerssen both speak of the quantity of starch in the axial row 
of cells in O. regalis, but in neither 0. cinnamomea nor O. Clay- 
toniana was this noticeable. As the ^gg approaches maturity 
the nucleus becomes large and distinct, and one or two nucleoli 




Fig. 197. — ^A, Young archegonium of O. 
cinnamomea, with the neck canal cell 
divided by a cell wall; B, a nearly ripe 
archegonium of the same species, X525. 



X THE HOMOSPOROUS LEPTOSPORANGIAT^ 355 

are present. The chromosomes are not conspicuous, a con- 
dition that we have seen before is not uncommon in the ^gg 
nucleus. 

A curious appearance was noted several times just before 
the archegonium seemed about to open, and after the formation 
of the ventral canal cell. This was the separation from the 
upper part of the Qgg of a small body containing what looked 
like a nucleus. Whether this is something analogous to the 
"polar body" found in animal ova could not be determined. 

When the archegonium opens, the four rows of cells bend 
strongly outward, and frequently some of the terminal cells 
become detached. A large receptive spot is present, and the 
nucleus is smaller than in the younger o^gg, and contains more 
chromatin, and usually but a single nucleolus. 

Fertilisation 

The horizontal position of the archegonia, as they project 
from the sides of the midrib, makes it easier to follow the en- 
trance of the spermatozoid than is the case in most Ferns. The 
spermatozoids collect about the mouth of the freshly-opened 
archegonium, and soon one finds its way in. With the ciliated 
end down, it revolves rapidly, not seeming to be much impeded 
by the mucilage thrown out by the archegonium. Suddenly, 
with a quick movement, quite unlike the slow worm-like move- 
ment seen in most Ferns, it slips through the neck into the cen- 
tral cavity, where its movement is resumed. After about three 
or four minutes it disappears, and has presumably penetrated 
the tgg. Other spermatozoids may make their way into the 
central cavity, but only one penetrates the ovum. The lower 
neck cells now approach, but not enough to prevent the entrance 
of other spermatozoids. Within a few hours the inner walls 
of the neck cells begin to show the brown colour that indicates 
that fertilisation has been accomplished. 

The Qgg quickly secretes a cellulose membrane, which pre- 
vents the entrance of the other spermatozoids. The egg nu- 
cleus moves towards the receptive spot at the time of fertilisa- 
tion, where the spermatozoid may be seen but little altered in 
form. It almost at once comes Into contact with the female 
nucleus, and the two then move toward the centre of the ovum. 
Here the spermatozoid gradually loses its coiled form and con- 



356 



MOSSES AND FERNS 



CHAP. 



tracts until it becomes oblong, and in close contact with the egg 
nucleus, in some cases looking as if it had penetrated the egg 
nucleus as it does in Onoclea (Shaw (2)). The process is a 
slow one, and in one case twenty-four hours after the entrance 
of the spermatozoid the two nuclei were still recognisable. 
Finally they are completely fused, and a single nucleus, with 
usually, perhaps always, two nucleoli is seen. No sign of a 
separation of the chromosomes of the copulating nuclei was 
observed. 

The Embryo 

The first division of the ovum is the same with respect to 
the archegonium as in Onoclea, i. e., the basal wall is parallel 




Fig. 198.— a. Vertical section of an eight-celled embryo of O. Claytoniana, X260.V 
Median longitudinal section of an older embryo of the same species, X260; C, 
two transverse sections of a somewhat younger embryo of O. cinnamomea, X260; 
St, stem apex; L, cotyledon; r, primary root; F, foot. 



with its axis ; but the quadrant wall is also parallel with this 
instead of transverse, although its position with reference to the 
axis of the prothallium is the same; so that the embryo-quad- 
rants, and the organs derived from them, are situated like those 
of the polypodiaceous embryo, with reference to the prothal- 
lium, but not to the archegonium. . , . 



THE HOMOSPOROUS LEPTOSPORANGIATJE 



357 



As in Onoclea the primary organs are established by the 
first two walls, and the next divisions form octants, but there is 
somewhat less regularity in tlie later divisions, in which respect 
Osmiinda is intermediate between the Polypodiace.'e and the 
Eusporangiatse. As in the former, the two epibasal quadrants 
develop stem and cotyledon, the hypobasal ones, root and foot. 
At this stage the cells of the young embryo contain but little 
granular cytoplasm, and there are large vacuoles. As the 
embryo grows older the granular cell contents increase in quan- 
tity. The subsequent divisions follow very closely those in the 
embryo of Onoclea, but are less regular, and the embryo retains 
for a longer time its original nearly globular form. 




Fig, 199.— Three sections of one embryo of O. cinnamomea in which the root (r) is 
especially well marked, X260. Lettering as in the last. 



The direction of growth of the cotyledon is determined in 
part by the first walls in its primary octants. The outer octant 
usually becomes at once its apical cell, and if its first segment 
is formed on the side next the octant wall, this throws the axis 
of growth very much to one side, so that the axis of the leaf 
may be almost at right angles to the median line of the embryo. 
Otherw^ise it nearly coincides with this. The original three- 
sided apical cell persists for a long time, and it could not be 
positively shown whether or not it was afterwards replaced by; 



358 



MOSSES AND FERNS 



CHAP. 



a two-sided one. The further development of the cotyledon 
corresponds almost exactly with Onoclea. It does not break 




Fig. 200. — A, Horizontal section of an advanced embryo of 0. Claytoniana, passing 
through the cotyledon and foot, X230; B, longitudinal section of the stem apex 
in a somewhat older embryo of O. cinnamomea, X460; C, transverse section of 
the apex of the primary root of the same, X460. 

through the calyptra until later, and in this respect shows its 
primitive character. The single vascular bundle of the petiole 




Fig. 201.— 'Transverse section of a prothallium of O. Claytoniana, showing the lateral 

position of the embryo {em), X75- 

approaches the collateral type, and is much like that of the 
cotyledon of Marattia. Stomata of the usual type occur on 



X THE HOMOSPOROUS LEPTOSPORANGIATJE 359 

both sides of the lamina. The development of the stem offers 
no peculiarities. The apical cell is of the tetrahedral form 
found in the mature sporophyte. 

The root is bulky, and the apical cell relatively small, with 
large segments, dividing less reg'ilarly than in Onoclca, and on 
the whole approaches most nearly to Botrychiiun. The form 
of the apical cell is like that of Onoclca or Botrychium, and is 
interesting because in the later roots this is replaced by another 
type, so that this w^ould indicate that the three-sided form 
found in so many cases is the primitive condition. The vas- 
cular bundle is diarch. 

The foot is very large, and while formed originally from 
the upper hypobasal quadrant, it encroaches more or less upon 
all the others. Very early its 
cells cease to show any regular 
order in their divisions, and di- 
vide more slowly than the other 
cells of the embryo, so that they 
become decidedly larger. The 
cells lose much of their proto- 
plasm as they increase in size, 
and serve simply as absorbent 
organs. They are in close con- 
tact with the prothallial cells, 
and crowd upon them until the p,^, ^o.—Young sporophyte of o. 

foot penetrates deep into the Claytoniana, stiU attached to the 

prothallium, whose cells it par- ^^^^ ^ '"°^' ^ * 

tially destroys. It is upon the large development of the foot, 
whose outer cells are sometimes extended into root-like exten- 
sions like those in Anthoccros, that the young embryo is main- 
tained so long at the expense of the prothallium. 

Frequently more than one embryo begins to develop, and 
sometimes a number of archegonia may be fertilised; but no 
cases were met with where more than one embryo came to 
maturity, although it is quite possible that this may occur. 

In all the Osmundacese the mature stem is a stout rhizome, 
which in the genus Todea may form an upright caudex, a metre 
or so in height. The bases of the stipes, are broadly winged 
and these sheathing leaf-bases persist for many years, com- 
pletely covering the surface of the stem. According to Faull 
(i)j who has made a very thorough study of the anatomy of 




36o 



MOSSES AND FERNS 



CHAP. 



the Osmundaceae, the stem usually bifurcates once, into branches 

of equal size, which may rarely fork once more. 

A section of the rhi- 
zome (Fig. 203, B), 
shows a massive cortex 
composed largely of dark 
sclerenchyma, but the in- 
ner cortex is parenchym- 
atous. The central cyl- 
inder is bounded by an 
endodermis, within 
which are from one to 
four layers of cells con- 
stituting the pericycle. 
FauU ( ( I ) , p. 7) was un- 
able to verify Strasburg- 
er's statement, that both 
the endodermis and peri- 
cycle in Osmunda, as in 
the other Ferns examined 
by the latter ((11), p. 
449), are of cortical or- 
igin. 

Inside the pericycle is 
a continuous cylinder of 
phloem, whose outer cells 
constitute the proto- 
phloem. The phloem 
proper consists mainly of 
sieve-tubes of large size 
and with conspicuous 
sieve-plates upon their 
lateral faces. The so- 





Clay' 



Fig. 203. — Upper part of a sporophyll of O. ^ 

toniana, X2; sp, sporangia; B, section of the Called "qUCrgeStrecktC- 
rhizome of O. regalis, showing the arrange- zeUen" of ZcUCtti TFis" 
ment of the vascular bundles, X4 (after . 

De Bary). 204, qu) are considered 

by Faull to be sieve-tubes. 

The woody strands form a reticulate cylinder, and in cross- 
sections of the stem appear as a circle of horse-shoe shaped 
masses of wood lying inside the phloem, and separated from 
each other by the medullary rays. The tracheary tissue con- 



THE HOMOSPOROUS LEPTOSPORANGIATJE 



361 



sists of small ringed and spiral elements constituting the proto- 
xylem, and larger scalariform metaxylem tracheids. In O. 
cinnaniomea, Faull found an internal endodermis and traces of 
internal phloem, which are ((uite ahsent in the other species, 
where the xylem-masses are in direct contact with the ])ith. 
Faull considers the condition in O. ciiinanioiiica as the primitive 
condition from which the type found in the other species has 
been derived by a suppression of the inner phloem and cnrlo- 
dermis. 

A. B. 




en. 
.pa. 

"■•pli. 
-xsh. 



o 






[© 



o 



-X. 



iec35 



'<^ 



o 



Fig. 204. — Osmunda regalis. A, Part of the central cylinder of the rhizome, X250; 
B, a sieve-tube, more highly magnified. (After Zenetti.) 

The leaf traces (Faull (i), p. 20) pass very obliquely 
through the cortex into the leaf base. They are concentric in 
structure. The protoxylem is situated on the inner face of the 
xylem strand and is continuous with that of the stem. Each 
leaf trace is surrounded by a sheath of colourless cells. 



The Leaf 

The origin of the leaves is the same as in the Polypodiaceae, 
but the young leaf grows from a three-sided apical cell much 



362 MOSSES AND FERNS chap^ 

like the stem (Bower (ii), Klein (2)), and the young leaf is 
more conical than in the Polypodiacese. In the very young 
leaf, according to Bower, one side of the apical cell is always 
directed toward the stem apex, and never one of the angles. 
In the presence of a three-sided apical cell, as well as its more 
cylindrical form, there is an approach to Botrychium. The 
further development of the leaf is like that of the pinnate leaves 
of the Marattiacese or Polypodiacese, with which they agree 
also in the strongly circinate vernation. The leaves are always 
pinnately divided, and are similar in all the species, and the type 
of venation is the same. While in all species of Osmunda and 
in Todea harhara, the structure of the leaf is quite like that of 
Polypodiacese, the other species of Todea (Leptopteris) have 
the lamina of the leaf reduced to two or three lavers of cells, and 
there are no stomata. The texture of the leaves in these forms 
is filmy, like that of Hymenophyllwn, 

The petiole is traversed by a single large vascular bundle, 
which in section is crescent-shaped and in structure concentric, 
with the elements like those of the Polypodiacese, but the endo- 
dermis is not so clearly differentiated; and close to the inner 
side of the bundle are numerous mucilage cells, recalling the 
tannin ducts of Angiopteris. A further point of resemblance 
to the Marattiacese is the presence of stipular wings at the base 
of the petiole. The chaffy scales (paleae) so common in the 
Polypodiaceae are quite wanting, But hairs are developed, often 
in great numbers. Thus in O. cinnamomea the young leaves 
are covered completely with a felted mass of hairs, recalling 
those in some of the Cyatheacese. Some of these are gland- 
ular. The sterile leaves and sporophylls are either very much 
alike, as in Todea, or the sporophylls may be very different. 
An extreme case is seen in O. cinnamomea, where the whole 
sporophyll is devoted to the development of sporangia. In 
this species, as well as 0. Claytoniana, the sporophylls develop 
first and form a group in the centre of a circle of sterile leaves. 
In O. cinnamomea the sporophylls develop no mesophyll, and 
die as soon as the spores are scattered. 

The Root 

The roots of the mature sporophyte differ very markedly 
from those of the other Leptosporangiatse, and have been the 



THE HOMOSPOROUS LEPTOSPORANGIATJE 



363 



subject of numerous investigations, but there still is a good 
deal of diversity of opinion as to their exact method of growth. 
Bower ((11), p. 310) states that in O. rcgalis there may be a 
single apical cell, such as exists in the first root of O. Claytoni- 
ana and O. cinnamomea, but that it never shows the regular 
segmentation of the typical leptosporangiate root, and it may 
be replaced by two or three similar initials. In Todea harhara 
he found four similar initials, and in no case a single one, 
although Van Tieghem and Douliot ((5), p. Z?^) ascribe to 
this species a single three-sided apical cell.^ 



B 





Fig. 205. — A, Longitudinal section through the root apex of 0. cinnamomea ; i, young 
tracheids, X200; B, cross-section of root apex of 0. Claytoniana, X200. 

Osmimda cinnamomea (Fig. 205, A) show^s a single very 
large initial, more or less triangular in form when seen in pro- 
file, but with the point sometimes truncate. Transverse sec- 
tions show that it is really a four-sided pyramid. The young 
segments are very large, and it is possible that these may some- 
times assume the role of initials. Owing to the slowness and 
irregularity of cell division it is difficult to trace the limits of 
the segments beyond the youngest ones. They usually form 



* Lachmann (i) asserts, however, that he found a group of initials such 
as Bower describes. 



364 



MOSSES AND FERNS 



CHAP, 



a spiral, but cases were sometimes encountered where the seg- 
ments were apparently cut off in pairs from opposite sides of 
the initial cell. The root-cap arises in part from special seg- 
ments cut off from the outer face of the apical cell, but also in 
part from the outer cells of the lateral segments, as in the Eu- 
sporangiatae. The separation of the tissue system follows 
much as in Botrychium. The central cylinder is large and oval 
in section, but with poorly-defined limits, and it is not possible 
to state positively whether it owes its origin exclusively to the 
innermost cells of the segments. The large central tracheae, 
as in Adiantum, are very early distinguishable. O. Claytoni- 
ana agrees on the whole with 0. cinnamomea, but the divisions 




Fig. 206. — Osmunda regalis. A, Section of young sporophyll passing through three 
very young sporangia; B, longitudinal section of an older sporangium; t, the 
tapetum, X325 (after Bower). 



are much more regular, and it approaches nearer the typical 
leptosporangiate type, both in the arrangement of the young 
tissues and in the structure of the fully-developed vascular 
bundle, which closely resembles that of the Polypodiaceae, and 
differs from the investigated species of Osmunda and Todea in 
the better development of the endodermis, and in having the 
pericycle of but one or two layers. The vascular cylinder of the 
root is typically diarch like that of the Polypodiaceae, but ex- 
ceptionally (Faull (i), p. 22), it may be triarch. 

The roots arise regularly, two at the base of each leaf 
(Lachmann (7), p. 118), and their bundles connect with those 
of the stem near the bottom of the elongated foliar gap in its 
vascular cylinder. 



THE HOMOSPOROUS LEPTOSPORANGIATJE 



36= 



The Sporangium 

The sporangia in Osnmnda are produced upon sporophylls 
that closely resemble those of Bofryclihun or H elminthostachys , 
but in Todea they occur upon the backs of the leaves, as in 
most Ferns. In structure and development they are intermedi- 
ate between the true leptosporangiate type and the eusporangi- 
ate. So far as they have been investigated they all correspond 
very closely. The origin of the sporangia is almost identical 
with that in Botrvchium, and more than one cell may take part 






Fig. 207. — A, Pinnule of a fertile leaf of Todea (Leptopteris) hymenophylloides, X2; 
B, fertile pinnule of Osmunda Claytoniana, X3; C-E, three views of the ripe 
sporangium of O, cinnamomea, X40; F, G, sporangia of Todea hymenophylloides, 
X40; r, annulus. 



in their formation (Bower (ii); Goebel (17)). Bower 
says: ''In all cases, however, one cell distinctly takes the lead, 
and this w^e may call the initial cell (Fig. 206, A) ; but the 
arrangement of its division wall does not, as in the true lepto- 
sporangiate Ferns, conform to any strict plan ; the initial cells 
are oblong, seen in vertical section, and the first divisions are 
longitudinal, so as to meet the basal wall : both in the segment 
thus cut off and in the central cell, periclinal or sometimes 
oblique divisions may take place, so that a considerable bulk of 



366 



MOSSES AND FERNS 



CHAP. 



tissue is formed, in the projecting apex of which a single large 
cell occupies a central position." As in Botrychium the arche- 
sporium is derived from a single hypodermal cell, which ap- 
proaches more or less the tetrahedral form of the true Lepto- 
sporangiates, but shows a good deal of variation. As in these 
the wall of the sporangium is only one-layered, and the tapetum 
ordinarily two, but occasionally three-layered. The fully-de- 
veloped sporangium is in shape much like that of Botrychium 
Virginianum, and has a very short massive stalk. Like Hel- 
minthostachys and Angiopteris, it opens by a vertical cleft, and 
like the latter there is a rudimentary annulus consisting of a 
group of thick-walled cells (Fig. 207, r). 



The GleicheniacetE 

These comprise about twenty-five species of tropical and 

sub - tropical Ferns, 
which may be all placed 
in two genera (Di^ls 
( I ) ) — Stromatopteris, 
with a single species 5'. 
moniliformis and 
Gleichenia with about 
25 species. The best 
known is G. dichotoma, 
an extremely common 
Fern of the tropics of 
the whole world. It has 
very long leaves, which 
fork repeatedly, and 
may be proliferous from 
the growth of buds de- 
veloped in the axils of 
the forked pinnae. 




X4; 



Fig. 208. — Gleichenia pectinata. Prothallia, 

B, a large prothallium seen from below, show- 
ing a dichotomy of the apex; C, the young 
sporophyte attached to the prothallium. 



The Gametophyte 

The development of the prothallium has been studied by 
Rauwenhoff ( i ) , and shows some interesting points in which it 
is intermediate between the Osmundacese and the other Lep- 
tosporangiatse. The spores of Gleichenia are usually tetra- 



THE HOMOSPOROUS LEPTOSPORANGIATJE 



367 



hedral, and contain no chlorophyll. When the ripe spores are 
sown, after a few days the oil-drops become much smaller but 
more numerous, and the first chloroplasts become evident. 
The latter increase in number and size, and small starch grains 
are developed. The exospore is ruptured in from two to three 
weeks from the time the spore is sown, and the spore contents 
surrounded by the intine project through the opening. The 
first wall usually separates the first rhizoid, which, like that of 
Osmiinda, often contains a good deal of chlorophyll, from the 
larger prothallial cell. As a rule the development of the pro- 
thallium corresponds closely to that of the Polypodiaceae, but 




Fig. 209. — Gleichenia pectinata. A, Ripe archegonium; B, nearly ripe antheridium; i, 
surface view; 2, optical section; C, apex of open antheridium, showing the method 
of dehiscence; D, section of very young antheridium. All figures X about 250. 



it may have a midrib like that of Osmunda. The growth is 
normally from a two-sided apical cell, which is replaced later 
by marginal initials. A point of resemblance to Osuiunda is 
the abundant production of adventitious shoots, which are 
formed in numbers upon the margin or from the ventral sur- 
face, and may develop into perfectly normal prothallia. 

Rauwenhoff' s account of the sexual organs is not as com- 
plete as might be wished, but is sufficient to show some inter- 
esting points of resemblance to the Osmundaceae. The first wall 
in the antheridium cuts off a basal cell, and the next wall is 
somewhat like the funnel-shaped wall in the Polypodiacese. 



368 



MOSSES AND FERNS 



CHAP. 



The • dome-shaped wall next formed is here not so marked, 
being nearly flat.^ No definite cover cell is cut off, but the 
upper cell appears to divide by a single wall running obliquely 
over the apex, somewhat as in Osmunda. The divisions in 
the central cell offer no peculiarities, and the spermatozoids 
resemble those of other Ferns. The archegonia are formed on 
the forward part of the midrib, but are not confined to the 
sides, as in Osmund a. Apparently a basal cell is not always 
formed, but as to this and the much more important point, the 
number and character of the canal cells, Rauwenhoff says noth- 
ing definite. The neck is long and straight, like that of Os- 
munda and the Hymenophyllacese. 




Fig. 210. — A, Diagram of the tissues of the rhizome in Gleichenia flabellata, X8; B, 
section of the stele (somewhat diagrammatic) of G. pectinata, X26; C, part of 
the stele of G. dichotoma, X350. (All figures after Boodle.) 



In G. pectinata (Fig. 209) the resemblance of the anther- 
idium to that of Osmunda is much more striking than in the 
species studied by Rauwenhoff. The archegonium in this 
species showed a division of the nucleus of the neck canal cell. 

* Rauwenhoff's statement that the central cell of the antheridium con- 
tains chlorophyll, to judge from his Fig. 58, which illustrates this, is based 
upon a pathological case. The absence of chlorophyll from the central cells 
of the antheridium is a very constant character in all Archegoniates. 



THE HOMOSPOROUS LEPTOSPORANGIAT^. 



369 



The Embryo 

To judge from the few rather vague statements made by 
Rauwenhoff in regard to the embryo, this more nearly re- 
sembles the typical leptosporangiate type than it does Osmunda. 
The primary root has a large and definite three-sided apical cell, 
and the divisions in the segments are very regular. 

The Adult Sporophyte 

Poirault ( i ) and Boodle (3) have made a study of the stem 
of various species of Gleichenia, which differs a good deal from 




Fig. 211. — Gleichenia flabellata. Development of the sporangium; A, B, X300; C, 

Xiso. (After Bower.) 



that of Osmunda, and approaches that of the Hymenophyllaceae 
and Schizseaceae. A single axial bundle traverses the stem, and 
is separated from the sclerenchymatous cortex by a distinct en- 
dodermis. Within the latter is a pericycle of several layers 
of cells, within which is a continuous zone of phloem containing 
large and small sieve-tubes, and phloem parenchyma. Within 
the phloem are also secreting cells. The whole central part of 
the stem, except in G. pectinata, is occupied by bundles of large 
scalariform tracheids separated by parenchyma (Fig. 210, C). 
The single bundle traversing the petiole is much like that of 



370 



MOSSES AND FERNS 



CHAP. 



Osmunda, and the lamina of the leaf does not show any peculi- 
arities. In G. pectinata (Boodle (3) ) , the stele is a hollow cyl- 
inder with both internal and external phloem and endodermis 
(Fig. 210, B). 

The Sporangium 

The development of the sporangium has been studied by 
Bower (19). The young receptacle begins to develop while 
the leaf is still tightly coiled. From the margin of the circular 
receptacle, and in some cases also from its upper surface, the 



B 



r- 





C. 



Fig. 212.— a, Pinnule of Gleichenia dichotoma, showing the position of the sori (j), 
X4; B, ventral; C, dorsal view of the ripe sporangium, X85. 



young sporangia arise as small conical outgrowths. Each spo- 
rangial outgrowth undergoes a series of regular segmentations 
resulting in a central, nearly tetrahedral, sporangial cell, from 
which successive segments are cut off which give rise to the 
short, massive stalk of the sporangium. Finally a periclinal 
wall is formed resulting in the archesporium. The further de- 
velopment is much like that of Osmunda, except that the inner of 
the two layers of tapetal cells become very large and their nuclei 



THE HOMOSPOROUS LEPTOSPORANGIATJE 



371 



may divide (Fig. 211). At this stage there is a marked re- 
semblance to the sporangium of Angioptcris, and Bower calls 
attention to the similarity in form between the sorus of Gleich- 
enia and that of the Marattiacese. The walls of the inner 
tapetal cells are finally absorbed. The number of sporogenous 
cells is large, the number of spores in G. Hahcllata amounting 
sometimes to over 800. 

In G. dichotoina (Fig. 212) the sporangia form rounded 
naked sori above the terminal branch of a lateral vein. They 
are pear-shaped, with a very short stalk, and upon the outer 
surface is a nearly complete very distinct annulus composed of 




Fig. 213. — Matonia pectinata. A, Base of fertile pinna, X3; B, section of the sorus; 
C, open sporangium, X3S; D, section of rhizome, Xio. (A, B, after Diels; D, 
after Seward.) 



a single row of large thick-walled cells. This is interrupted 
at the top of the sporangium by three or four narrow thin- 
walled cells, and starting from this point and extending along 
the median line of the ventral surface are two rows of narrow 
cells, between which the sporangium opens. 

The Matoniace^ 



• The family Matoniacese is represented by the single genus 
Matonia (Fig. 213), with two species, M. pectinata and M. sar- 



Z72 MOSSES AND FERNS chap. 

mentosa, both of limited range, and confined to the Malayan 
region. The affinities of Matonia are probably with the 
Gleicheniaceae, rather than with the Cyatheacese, with which 
they were formerly associated. The large flabellate leaves of 
M. pectinata are much like those of some species of Gleichenia, 
and the arrangement of the sori is much the same. There is, 
however, a conspicuous umbrella-shaped indusium of firm tex- 
ture, and in their form and dehiscence the sporangia are more 
like those of the Cyatheacese. The development of the spo- 
rangium, according to Bower (19), is much like that of 
Gleichenia. 

The structure of the stem in Matonia pectinata (Seward 
(2) ) is very much like that of Gleichenia pectinata, but there is 
a second and sometimes a third cylindrical stele within the 
primary stele (Fig. 213, D). 

Zeiller (i) from a comparison of Matonia with the fossil 
genus Laccopteris, which occurs in early Jurassic beds, con- 
cludes that the two genera are very closely related, if not actu- 
ally identical, and represent the earliest forms of the Cyathe- 
acese, and that Matonia is the last remnant of a family now in 
process of extinction. 

The Hymenophyllace^ 

The Hymenophyllacese have been the subject of much dis- 
cussion on account of the assumption made by all the earlier 
writers that they were the most primitive of the Pteridophytes. 
This w^as based very largely upon the apparent resemblance 
between the delicate sporophyte of many of them and the leafy 
gametophore of the Mosses. More recent study of their de- 
velopment, especially the gametophyte, has led to a modification 
of this view, although it is still held by many botanists. It 
seems more probable that the peculiarities of both gametophyte 
and sporophyte are due to the peculiar environment of these 
plants, which grow only in very moist places, indeed are almost 
aquatic at times. They are for the most part extremely deli- 
cate Ferns of small size, and with few exceptions are tropical. 
Many are epiphytes, and these have the roots very poorly de- 
veloped or even entirely wanting. The leaves are, with few 
exceptions, reduced to a single layer of cells, except the veins, 
which gives them a striking resemblance in texture to the leaves 



THE HOMOSPOROUS LEPTOSPORANGIATJE 



373 



of some of the larger Mosses, e. g., species of Mniiim. Hooker 
( I ) reduces them all to three genera, which, however, are often 
further divided. Of these Loxsoma is represented by but one 
species, L. Ciinninghamii, a form which seems to be intermedi- 
ate in general characters between the Cyatheacese and the other 
Hymenophyllacese, but its life history and anatomy are not 
known. Of the other genera Hooker gives seventy-one species 
to Hymenophylhim and seventy-eight to Trichomanes.^ 

The Gametophyte 

The gametophyte is known more or less completely in sev- 
eral species of both Trichomanes and Hymenophyllum, The 




. r. 



Fig. 214. — Trichomanes Draytonianutn. Germination of the spores, X525; r, primary 

rhizoid. 



large spores germinate promptly, but their subsequent develop- 
ment is very slow. They contain chlorophyll and often begin 
to germinate within the sporangium, where they may often be 
found divided into three equal cells by walls radiating from the 
centre (Fig. 214). All of the cells begin to grow out into 
filaments, but usually only one of them develops into the pro- 
thallium, the others dividing only once or twice, and forming 
short brown rhizoids. In some species of Trichomanes^ e. g. 

*The number of species known now considerably exceeds this. 



374 



MOSSES AND FERNS 



CHAP. 



T. pyxidiferum (Bower (8)), the prothallium remains fila- 
mentous, and forms a densely branching structure very much 
like the protonema of some Mosses, but coarser in texture. 
Other species, however, e. g., T. alatum, produced flattened 
thalloid prothallia from branches of the filamentous forms, and 
Hymenophyllum always has a flat hepatic-like prothallium, 
which in its earHer stages, according to Sadebeck ((6), p. 
i6i), always develops a two-sided apical cell, and differs in no 
wise from that of other Ferns. These prothallia, however, 
remain single-layered throughout, although they reach an ex- 
traordinarily large size, and branch much more freely than 
those of most other Ferns (Fig. 215). The rhizoids are 
always very short and dark-coloured, and generally occur in 




s 



Fig. 2 IS- — Hymenophyllum (sp). A, Large prothallium of the natural size; B, part of 
the margin of one of the growing branches, showing two similar initial cells, Xi8o; 
C, a filamentous male prothallium derived from a bud, X6o. 



groups upon the margin only. The branching of the prothallia 
is either monopodial or dichotomous, and the latter method 
may be repeated a number of times. They may live for an in- 
definite time apparently. The writer has kept prothallia of 
both Trichomanes and Hymenophyllum for nearly two years, 
at the end of which time they showed no diminution of vigour. 
They form ordinary adventitious shoots, but there are also 
special gemmae developed in many of them, often in great num- 
bers. In an undetermined species of Hymenophyllum col- 
lected In the Hawaiian Islands (Fig. 216) these gemmae oc- 
curred very abundantly upon prothallia that had ceased to form 
sexual organs. A marginal cell grows out and curves upward, 



THE HOMOSPOROUS LEPTOSPORANGIAT^ 



375 



and the tip is cut off by a transverse wall from the basal cell. 
In the terminal cell are next formed a series of vertical walls, 
which transforms it into a row of cells extended at right angles 
to the axis of the pedicel. One of the central cells now bulges 
out laterally, and this papilla is cut off by an oblique wall and 
forms the beginning of a short lateral branch, so that the fully- 
developed bud has somewhat the form of a three-rayed star, 
and in this condition becomes detached and growls into a new 
prothallium. The prothallia formed in this way often do not 




Fig, 2i6. — Hymenophyllum (sp). Margin of a prothallium with numerous gemmae k; 
X8s; B, a young gemma, X260; st, its stalk. 



develop a flat thallus, but may remain filamentous, and each 
ray may produce antheridia either terminally or laterally (Fig. 
215, C). In case a flat thallus is formed, only one or some- 
times two of the rays grow out in this form, the other having 
only a limited growth, and terminating in a short rhizoid. In 
short, the process is very similar to that in the germinating 
spores. 



376 



MOSSES AND FERNS 



CHAP. 



The Sexual Organs 

Bower (8) has investigated the structure of the anther- 
idium in Trichomanes, and Goebel (lo) in both Trichomanes 
and Hymenophyllum. My own study of their development 
has been confined to an undetermined species of Hymenophyl- 
lum from the Hawaiian Islands, but the results of my observa- 
tions agree entirely with those of other observers. The anther- 
idia arise mainly upon the margin of the prothallium, or upon 
the ends of the filamentous ones. After the mother cell is cut 






Fig. 217. — Hymenophyllum (sp). Development of the antheridium, X260. A, D, 
From living specimens; E, microtome section; B i, C 2, D i, optical sections; 
B 2, C I, D 2, surface view of the same. 



off, there is usually formed another transverse wall, by which 
a short pedicel is produced. A funnel-shaped wall does not 
ever seem to be formed, but the next division walls are more 
like those in Osmunda, and extend only part way round the 
circumference of the mother cell. After a varying number of 
basal cells are thus formed, a dome-shaped wall arises, separat- 
ing the central cell. This wall is not so convex, as is usually 
the case in the Polypodiaceae, and in this respect, as well as the 
form of the wall cells, the antheridium resembles that of Gleich- 



THE HOMOSPOROUS LEPTOSPORANGIAT^ 



Z77 



enia. In the Hymenophyllaceae no cap cell is formed, but as in 
Osmunda and Gleichenia, the upper cell is divided by walls 
running over the apex. The divisions in the central cell and 
the structure of the spermatozoids, so far as these have been 
studied, correspond with those of the other Leptosporangiatae. 
A single archegonial cushion is not formed, but the arche- 
gonia occur in small groups at different points upon the margin. 
Goebel ( lo) has shown, however, that these archegonial groups 
arise first near the growing point of the prothallial branch, and 
that they are simply separated by the intervention of zones 
of sterile tissue. At the point where they arise the prothallium 
becomes more than one cell thick, and in all cases where the 
development could be certainly followed, the archegonium 
arose from one of the ventral cells, and never directly from a 
marginal cell. The details of the development have not been 




Fig. 2i8. — Part of the filamentous prothallium and archegoniophores of Trichomanes 
rigidum. (After Goebel.) 



followed, and whether there is any division of the neck canal 
cell is not known. The neck is straight, as in Osmunda and 
Gleichenia. 

In Trichomanes the archegonial meristem (archegonio- 
phore) may be formed as a short branch, directly upon the fila- 
mentous prothallium. 

The lateral walls of the prothallial cells are in all the species 
thicker than is the case in most Ferns, and there are distinct pits 
in them. In the rhizoids a parasitic fungus is frequently 
found. 

The embryogeny is almost unknown (Janczewski (2) ), but 
the first divisions and the very young sporophyte correspond 



378 



MOSSES AND FERNS 



CHAP. 



closely with those of the other Leptosporangiatae. The coty- 
ledon is simple with a single median vein, and a root is present 
in all species yet examined. 

The Mature Sporophyte 

Prantl ( i ) has given a very complete account of the struc- 
ture of the mature sporophyte, and Bower ( 1 1 ) has added to 
this by a careful study of the meristems of the different organs. 
From the investigations of the latter it seems that here, as in 
nearly all other Ferns, the stem apex has the usual three-sided 




Fig. 219. — Pinna of the leaf of Hymenophyllum recurvum, X3; B, part of rhizome (r) 
and leaf of Trichomanes parvulum, X3; C, pinna of the leaf of Trichomanes 
cyrtotheca, X3; D i, trumpet-shaped indusium of the same, X4; 2, section of the 
indusium (td) with the central sorus, X 5 ; ^, the sorus. 



initial cell, but only a small part of the segments give rise to 
leaves, which are arranged in two ranks. 

The stem in all investigated Hymenophyllacese is mono- 
stelic, and one leaf-trace passes to each leaf. The cortex is 
usually largely made up of sclerenchyma, especially the inner 
cortex. In Hymenophyllum recurvum (Fig. 220), the axial 
vascular bundle is strictly concentric. Occupying the centre 
is a curved band of tracheary tissue, the small central tracheids 
being the protoxylem. Around the xylem is a continuous zone 



X 



THE HOMOSPOROVS LEPTOSPORANGIAT^ 



379 



of phloem, separated from the endodermis by a broad pericycle. 
In other species of HymenopJiylliim, Boodle ( i ) found a dif- 
ferent arrangement of the xylem and phloem. In some cases, 
e g., H. scabnim, there are two xylem plates, with the proto- 
xylem elements in the conjunctive tissues between them. 

In Trichomanes there is also a good deal of variation. Fig. 
220, B, shows the structure in T. venosiim, a small species from 




Fig. 220. — 'A, Section of the rhizome of Hymenophyllum recurvum, X about 40; B, 
rhizome of Trichomanes venosum, X about 75; C, stele of B, more highly mag- 
nified; D, root of Hymenophyllum recurvum, X about 75; E, stele of the root 
more highly magnified. 



Australia and New Zealand. The structure of the stem dif- 
fers from that of Hymenophyllum recurvum, mainly in its 
greater delicacy. The sclerenchyma of the cortical region is 
less developed, and the concentric axial cylinder corresponding 
to its much smaller size has both the xylem and phloem reduced 
in amount. 

In the stouter species, like T. radicans, the amount of wood 



38o MOSSES AND FERNS chap. 

is much greater. According to Boodle (1. c. Fig. 24), there 
are two or three protoxylems, accompanied by parenchyma 
cells, surrounded by a massive ring of large tracheids. There 
is an approach in this species, and still more in T. reniforme, 
to the form characteristic of Hymenophyllum scabrum and its 
allies. In the small species, T. muscoides, apparently by reduc- 
tion, the stele becomes collateral, and this, according to Prantl 
( ( I ) , p. 26) , is the rule in the sub-genus H ennphlehium, where 
the xylem lies on the ventral side of the stem, the phloem on the 
dorsal side. The pericycle, at certain points, shows clearly its 
common origin with the endodermis. Van Tieghem (3) con- 
siders that there is a double endodermis, and that no true peri- 
cycle is present. In T. lahiatum (T. microphyllum) Giesen- 
hagen ( i ) found the bundle reduced to a single tracheid sur- 
rounded by four or five parenchyma cells immediately within 
the endodermis. The reduction is carried still further in T. 
Motleyi, where tracheary tissue has entirely disappeared from 
both stem and sterile leaf. In the sporophylls, however, trach- 
eary tissue is present (Karsten (2), p. 135). 

The Leaf 

The observations on the earliest stages of the leaf are very 
incomplete, but in some cases at least a two-sided apical cell is 
present. In those with palmately lobed or entire kidney-shaped 
leaves, the later growth is marginal, and of the same type found 
in similar leaves among the Polypodiaceae. The venation in 
these forms is exclusively dichotomous, in those with pinnate 
leaves, e. g., Trichomanes radicans, this is only true of the last 
formed veins. 

With the exception of a very few species, e. g., T. reniforme, 
H. dilatatiim, where the mesophyll of the leaves is three to four 
cells thick, the whole lamina, with the exception of the veins, is 
single-layered, and of course stomata are completely absent. 
The form of the leaf is either pinnate, as in the larger species 
of Trichomanes and Hymenophyllum (Fig. 219), reniform 
{T. reniforme) , or palmately divided (T. parvulum, Fig. 219, 
B). The smaller veins, as in other Ferns, have collateral vas- 
cular bundles, and in the smallest ones the xylem may be re- 
duced to a single row of tracheids. The latter may be spiral, 
reticulated, or scalariform. In the phloem Prantl could not 



X THE HOMOSPOROUS LEPTOSPORANGIATJE 381 

distinguish any well-marked sieve-tuljes, but it was mainly com- 
posed of bast fibres and cambiform cells, and in Hcniiphlcbium 
{Trichomanes) Hookcri the phloem is absent from the very 
much reduced smaller veins. This is j)ossibly an intermediate 
condition between the normally developed bundles of the veins 
of most species and the so-called pseudo-veins, in which there 
is no tracheary tissue developed, but which in their origin cor- 
respond to the ordinary veins. The petiole always has a single 
vascular bundle, usually of typical concentric structure, but in 
the section Hcuiiphlchium Prantl states that it is collateral. 
The ground tissue of the petiole is largely composed of scleren- 
chyma like that of the stem. 

The Roots 

The development of the roots has been studied only in a 
very few species. Bower (11) states that in T. radicans and H. 
demissiun it ''conforms to the normal type for the root of lep- 
tosporangiate Ferns, as described by Nageli and Leitgeb," but 
does not go into details, and Prantl makes an equally brief 
statement. While lateral roots are completely wanting in the 
section Hemiphlehhim, where their place is taken by leafless 
branches, in most of the other forms they are developed in 
considerable numbers. There is, according to Prantl, great 
variation in the arrangement of the parts in the vascular cyl- 
inder. Thus while all the species of HynicnophyUum have 
diarch bundles, that of Trichomanes pyxidifenini is monarch, 
while in one species, T. bracJiypits, as many as nine primary 
xylem masses are found. The Marattiaceas alone, among the 
other Ferns, show such great variability. 

Trichomes occur, but not so abundantly as in most of the 
Leptosporangiatse. They have usually the form of hairs, 
which are either temporary (those formed on the margins of 
the young leaves) or persistent for a longer time, like those 
that cover the end of the stem apex and bases of the petioles in 
many species. 

The Sporangkim 

All of the Hymenophyllaceas agree closely in the position of 
the sporangia, whose development has, however, been studied 
in detail only in Trichomanes ; but from the close correspond- 



382 



MOSSES AND FERNS 



CHAP. 



ence in other respects it is not likely that Hymenophyllum dif- 
fers essentially from the latter. The sorus occupies the free 
end of a vein, which often continues to grow for a long time 
in Trichomanes, and forms a long slender placenta or colum- 
ella, upon which the sporangia arise basipetally. While the 



sp. 






Fig. 221. — Trichomanes cyrtotheca. Development of the sporangium, X22S. A, 
Longitudinal section of very young receptacle with the first sporangia isp) ; B-D, 
successive stages of development seen in longitudinal section; F, horizontal section 
of nearly ripe sporangium; r, the annulus. 



receptacle Is still very young the tissue of the leaf immediately 
about it forms a ring-shaped ridge, which grows up in the form 
of a cup-shaped indusium, which either remains as a tube 



X THE HOMOSPOROUS LEPTOSPORANGIATJE 383 

(Trichomancs) or is divided into two valves (Hymenophyl- 
him). Many species of the former genus, however, show an 
intermediate condition, with the margin of the indusium deeply 
two-lipped. 

The first sporangia arise at the top of the placenta (Fig. 
221), but the apex itself does not usually develop into a spo- 
rangium. After the first sporangia have formed, new ones 
continue to develop. Near the base of the placenta a zone of 
meristem is formed, which constantly contributes to its growth, 
and the young sporangia arise from the surface cells formed 
from this meristem. The mother cell is very easily distin- 
guished by its larger size and denser contents. About every 
third cell seems to develop a sporangium, but this probably is 
not absolutely uniform. The first wall is usually nearly vertical, 
and cuts off a narrow segment from one side of the mother cell 
(Fig. 221, A). This in most cases examined was next fol- 
lowed by a wall almost at right angles, separating a small basal 
cell. After these preliminary divisions, which form the very 
short stalk, the next divisions are exactly as in the Polypodi- 
aceae, and give rise to the central tetrahedral cell with the four 
peripheral ones. Prantl ( (i), p. 39) states that the first divi- 
sions of the cap cell are also spirally arranged. In T. cyrto- 
theca (Fig. 221) the tapetum is massive, and composed 
throughout of two layers. The archesporium divides into 
eight cells, whose further history is the same as in other Ferns. 
The annulus in the Hymenophyllacese is large, and situated 
much as in Gleichcnia. According to Prantl, it arises in part 
from the cap cell and partly from numbers one and three of the 
primary peripheral cells. Where the young sporangium is cut 
longitudinally (Fig. 221), the annulus cells are at once recog- 
nised by their larger size, especially upon the dorsal side. 
Their radial and inner walls become very thick, and a horizontal 
section (Fig. 221, F) shows that the annulus is not complete, 
but is interrupted on the inner side wdiere the stomium is formed. 

Apogamy and Apospory 

Both of these phenomena have been discovered by Bower 
(8) to occur not infrequently in Trichomanes, and probably 
further investigations will reveal other instances. Apogamy 
was common in T. alatum, in which species archegonia w^ere 



3,84 



MOSSES AND FERNS 



CHAP. 



not seen at all, and the origin of the young sporophyte was un- 
mistakably non-sexual. Prothallia, arising directly from the 
leaf, or from the sporangial receptacle, were found to be a com- 
mon phenomenon in the same species. 

The Schiz^ace^ (Diels (l)) 

The Schizaeaceae include about sixty species belonging to 
five genera. The very characteristic sporangia have a terminal 
annulus, which forms a sort of crown at the apex. Some of 
them, like SchizcBa pusilla and Trochopteris elegans, are very 

^- B. 





Fig. 222. — A, Prothallium of Aneimia Phyllitidis, Xi8o; B, female; C, male, prothallia 
of Schisaea pusilla, X30 (A after Bauke, B, C, after Britton & Taylor.) 

small and delicate plants. In the largest species of Lygo- 
diimt the slender twining fronds may reach a great length. Ac- 
cording to Hooker (2), the New Zealand species L. articu- 
latum, may reach a length of 50 — 100 feet. 



The Garnet ophyte 

According to Bauke (2), the prothaUium in Lygodium, 
Aneimia, and Mohria is much like that of the Polypodiaceae, 
except that in the two latter genera (Fig. 222), the growing 
point is at one side." The spores are tetrahedral, and contain 
no chlorophyll until after germination has begun. The germ- 



THE HOMOSPOROUS LEPTOSPORANGIATM 



38s 



ination is like that of the Polypodiacese, and a filament is first 
formed, after which the flat prothallium grows for a time by 
a single apical cell, which is finally replaced by a group of mar- 
ginal cells. In A}ieimia and Mohria the growing point lies on 
one side, so that the prothallium is not heart-shaped. In Ly- 
godiiim, however, the prothallium has the ordinary form. 

The development of the antheridia has been studied by Kny 
(4) in Anemiia hirta. The only difference between this and 




Fig. 223. — Aneimia hirsuta. A, Section of the rhizome, X30; B, part of the central 

region, X300. 



the normal antheridium of the Polypodiaceae is that in Aueiuiia 
the first wall is always flat instead of funnel-shaped, and the 
basal cell of the antheridium is therefore disc-shaped. The 
archegonia appear to correspond exactly with those of the Poly- 
podiaceae. 

The genus Schiccra, to judge from 5^. pusilla (Britton and 
Taylor (i)), and S. dichotoma (Thomas (i)), differs mark- 



386 



MOSSES AND FERNS 



CHAP. 



edly from the other genera in the form of the prothalHum, 
which is filamentous and extensively branched, resembling very 
closely that of certain species of Trichomanes (Fig. 222, B, C). 
The antheridia resemble those of Aneimia, but the archegonium 
has the straight neck found in the lower Leptosporangiatse. 

The Sporophyfe 

The tissues of the sporophyte in Lygodium and Schiscea are 
much like those of Gleichenia and the Hymenophyllacese. As 
in these the stem as well as the petiole is traversed by a single 




Fig. 22/^.— -Lygodium Japonicum. A, Pinnule, Xs; s, the sporangial segments; B, 
horizontal section of one of the latter showing the sporangia, sp, X14; C, a single 
sporangium, showing the terminal annulus (r), X65; cross-section of the petiole, 
X65. 



concentric vascular bundle. In most species of Aneimia and 
Mohria the bundles of the stem form a cylindrical network like 
that of the Polypodiacese. The stem bundles are concentric, 
as are those of the petiole and larger veins in all but Schiscea, 
which Prantl ( (5), p. 23) states has collateral bundles through- 
out, except in the stem. The small veins have collateral bun- 



THE HOMOSPOROUS LEPTOSPORANGIAT^ 



387 



dies as in other Ferns. Sclerenchyma is largely developed, 
especially in the petioles, where the whole mass of ground tissue 
in Lygodium (Fig. 224) is composed of this tissue. 

In one section of Anciuiia the stele (Fig. 223) has the form 
of a continuous tulje with both external and internal phloem 
and endodermis (see also Boodle (2)). 

The leaves are pinnate in all the forms except a few species 
of Schi::cca. Lygodium, as is well known, shows a continuous 
growth at the apex of the leaf, something like GleicJienia, but 
here the primary apex retains its meristematic condition, and 
the extremely long and slender axis of the leaf twines about its 
support like the stem of many climbing plants. The sporo- 




FiG. 225. — Aneimia hirsuta. A, Sporophyll, showing the two fertile pinnae, sp.; B, 
segment of the fertile pinna, enlarged; C, D, sporangia, X about 40. 



phylls are usually smaller than the sterile leaves, or where only 
portions of the leaf are sporiferous these are much contracted. 
The anatomy of the leaf corresponds closely wdth that of the 
other Ferns. The stomata, which are for the most part con- 
fined to the low^er side of the leaf, are always arranged in two 
parallel rows in Schizcca, and the peculiar stomata of Aneimia 
have already been mentioned. The trichomes are for the most 
part hairs. Only in Mohria do scales occur. 

In Scliizcca pusilla the sterile leaves are filiform, without 



388 



MOSSES AND FERNS 



CHAP. 



any distinct lamina. The fertile leaves are pinnately divided. 
In other species, e. g., S. dichotoma, the leaves are dichoto- 
mously divided, but the fertile leaf-segments are pinnate, as they 
are in .S. pusilla (Diels ( i ) ) . 

In Aneimia (Fig. 225) the two lower pinnae of the sporo- 
phyll are fertile, and in most species become very long-stalked 
and more divided than the sterile pinnae. The leaves arise from 
the dorsal side of the rhizome and in Lygodium, Prantl (5) 
states that they form but a single row. He also says that the 




Fig. 226. — A, Apex of a young, fertile leaf-segment of Aneimia Phyllitides, X200; 

B, transverse section of young fertile leaf-segment of Schizaea Pennula, Xioo; 

C, part of a similar section ot a somewhat older leaf, Xioo; sp, young sporangia; 
in, indusium. (All figures after Prantl.) 

roots are always diarch, like the Polypodiacese, but gives no 
further details of their growth or structure. 



The Sporangium 

The development of the sporangia has been carefully in- 
vestigated by Prantl (5) and in origin and arrangement they 
differ decidedly from the other Leptosporangiates, but approacli 
most nearly Osmunda, and among the eusporangiate Ferns 



THE HOMOSPOROUS LEPTOSPORANGIAT^ 



389 



show a certain likeness to Botrycliiuni. J he sporangia arise 
always in acropetal order from the apex of the terminal seg- 
ments (sorophore) of the sporophyll, and are strictly lateral in 
origin, not originating from epidermal cells, but from marginal 
ones. The young sporangium api)ears as a lateral outgrowth 
of the margin, exactly like a young pinna upon the main axis, 
and the young sorophore has the appearance of a young pinnate 
leaf, and at this stage recalls strongly the similar one in Bo- 
trychium. This is especially marked in Aneimia and Lygo- 





FiG. 227. — Cibotium Mcnziesii. A, Pinnule with the sori {s), X3; B, a single sorus 
showing the two-valved indusium, X9; C, a single sporangium, X80; r, the 
annulus; D, a paraphysis, X8o. 

dium, less so in Schiscea, where the sporangia are smaller, and 
the mother cells project much more strongly. The early divi- 
sions correspond closely with those of the Hymenophyllacese, 
and as there the tapetum is massive and two-layered, and the 
stalk of the sporangium very short. The wall Is derived in 



The divisions in the wall are too complicated to be explained without 
numerous figures. See Prantl's figures, Plate V.-VIII. 



390 



MOSSES AND FERNS 



CHAP. 



major part from the cap cell, which in all the forms becomes 
much more developed than in any other Ferns, and from it 
alone the apical annulus is derived. In Aneimia and Mohria 
the tissue of the tip of the leaf adjacent to the sporangia grows 
into a continuous indusium, which pushes them under to the 
lower side. In Lygodium (Fig. 224) each sporangium very 
evidently corresponds to a single lobe of the leaf segment, and 
has a vein corresponding to this. The pocket-like indusium 
surrounding each sporangium grows up about it much as the 
indusium of Trichomanes grows up about the whole sorus.. 






Fig. 228. — Alsophila Cooperi. A, section of the stipe, XiJ^; B, cross-section of leaflet, 
showing the sori, X20; C, open sporangium. 



The Cyatheace^ 

These are all Ferns of large size, some of them Tree-Ferns, 
10 metres or more in height. They occur in the tropics of 
both hemispheres, and some of them, e. g., Dicksonia antarctica, 
are also found in the extra-tropical regions of the southern 
hemisphere. They correspond so closely in all respects with 
the typical Polypodiacese that, except for the slightly different 
annulus, they might be placed in that family. In some forms, 



X THE HOMOSPOROUS LEPTOSPORANGIATJE 391 

e. g., AlsopJiila contaminans, the trunk is quite free from roots, 
and the leaves fall away, leaving very characteristic scars 
marked by the vascular bundles. In others, like Dicksonia ant- 
arctica, the whole trunk is covered with a thick mat of roots, 
thicker than the trunk itself. 

The prothallium is exactly like that of the Polypodiacese, 
so far as it has been studied (Bauke ( i ) ), except that in some 
species of Alsophila there are curious bristle-like hairs upon the 
upper surface. In the structure of the antheridia the Cyathe- 
acese are intermediate in character between the Polypodiaceai 
and the Hymenophyllacese. The characteristic funnel-formed 




Fig. 229. — A, Part of a sporophyll of Thyrsopteris elegans, X2; B, section of the 
sorus, Xio; C, leaflet, with two sori, of Cyathea microphylla. (A, B, after 
JCunze; C, after Hooker.) 



primary w-all of the former occurs here, but not until one and 
sometimes two preliminary basal cells are cut off, as in Os- 
munda or Hymenophylhim. The following divisions corre- 
spond exactly with those of the antheridium of the Polypodi- 
aceae, except that Bauke states that the cap cell, as well as the 
upper ring cell, may divide again. The dehiscence is effected 
either by the separation of an opercular cell or by the rupture of 
the cap cell. The archegonia are like those of the Polypodi- 
acese. In Cyathea medullaris Bauke figures a specimen, how- 
ever, where the neck canal cell is divided by a membrane (1. c. 
PL IX, Fig. 8). 

The first divisions in the embryo correspond with those of 
the Polypodiacese, but the further development of the young 
sporophyte is not known. 



39^ MOSSES AND FERNS chap. 

The position of the sori is that of the typical Polypodi- 
aceae, and sometimes a decidedly elevated placenta is present. 
The indusium is either cup-shaped (Cyathea), or bivalve, e. g., 
Cibotium (Fig. 229). In the latter the outer valve fits closely 
over the other like the cover of a box. The sporangia which 
are either long or short-stalked, although their development 
has not been followed, correspond so closely in the mature state 
to those of the Polypodiacese that there is little doubt that their 
development is much the same. The annulus is nearly or quite 
complete, but above the stomium in Cibotium Menmesii the cells 
of the annulus are broader but thinner-walled (Fig. 227, C), 
and Atkinson shows much the same appearance in C. Chamissoi. 
In the former species the stalk is long and composed of three 
rows of cells, as in typical Polypodiaceae, With the sporangia 
in this species are also numerous long paraphyses (Fig. 
227, D). 

The Parkeriace^ (Diets (i), Kny (6)) 

This family comprises but a single species, Ceratopteris 
thalictroides, a peculiar aquatic Fern of wide distribution in 
the tropics. Unlike most Pteridophytes, Ceratopteris is char- 
acteristically annual, although by the formation of adventive 
buds it may become perennial. 

The prothallia are usually dioecious, and the antheridia dif- 
fer from those of the typical Polypodiaceae in projecting but 
little above the surface of the prothallium. 

Except for the peculiarities due to its aquatic habit, in which 
respect it differs from all other homosporous Ferns, the growth' 
of the organs and structure of the tissues is similar to those of 
the Polypodiaceae, to which family Ceratopteris is often as-- 
signed. 

The development of the sporangium is essentially like that 
of the Polypodiaceae, but the annulus sometimes shows an in- 
complete development, probably correlated with the aquatic 
habit of the plant (Hooker (i), p. 174). 

The Polypodiace^ 

The Polypodiaceae may very aptly be compared to the stego- 
carpous Bryineae among the Mosses, inasmuch as like that 



THE HOMOSPOROUS LEPTOSPORANGIAT^ 



393 



group they give evidence of being the most speciaHsed members 
of the order to which they belong, and comprise a very large 
majority of the species. Most of them agree closely in their 
structure, which has been given in detail, and will not be re- 





FiG. 230. — A, Pinnule of Aspidium spinulosum, showing the sori {s) with kidney- 
shaped indusium, X2^; B, cross-section of a pinna from a young sporophyll of 
Onoclea struthiopteris ; s, sorus, X25. 



peated here. With very few exceptions the structure of the 
prothallium and sexual organs is like that of Onoclea, but one 
or two variations may be mentioned. In Vittaria (Britton and 
Taylor (2)), is found a type of prothallium recalling that of 



..-sp 






Fig. 231. — A, Polypodium falcatum. Pinna with sori, sp; natural size. B, Pteris 

aquilina. C, Asplenium filix-foemina, X3' 

Hymenophylhim, both in its large size and extensive branching. 
Its earlier stages show the ordinary development, but it later 
branches extensively, and, like Hymenophylhim, numerous 
groups of archegonia are formed upon one prothallium. Bod- 



394 



MOSSES AND FERNS 



CHAP. 



ies resembling the oil bodies of Liverworts are also met with in 
this genus. The sexual organs closely resemble those of the 
Polypodiacese, but the antheridia have a well-marked stalk, 
something like that found often in the Hymenophyllacese. 
Among the many genera and species aside from these, while 
there is extraordinary variety, the differences are all of second- 
ary importance, and consist mainly in the form and venation of 
the leaves and the position of the sporangia. The leaves range 
from the undivided ones of Vittaria or Scolopendrium to the 




• •* 



Fig. 232. — Platycerium alcicorne. A, Whole plant, much reduced; B, tip o£ a spo- 
rophyll, showing the crowded sporangia. (A, after Coulter; B, after Diels.) 



repeatedly divided leaves, usually pinnate, of such forms as 
Pteris aquilina. In some tropical epiphytic species, such as 
Asplenhim nidus, Platycerium, species of Polypodium, the 
leaves are arranged so that they form receptacles for collecting 
humus. In the two latter genera these leaves are very much 
modified, the two forms of leaves being familiar to all botanists 
m the common Platycerium alcicorne, where the closely over- 
lapping round basal ones are very highly developed. 



X THE HOMOSPOROUS LEPTOSPORANGIATJE 395 

The sporangia may almost completely cover the backs of 
the sporophylls, as in Platyccrimn (hig. 232), or more com- 
monly form definite sori, which may or may not have an in- 
dusium. Where the latter is present, it is either formed by the 
margin of the leaf, as in Adianttim or Pteris, or it may be a 
special scale-like outgrowth of the lower side of the leaf. In 
such cases it is a membranaceous covering of characteristic 
form. Thus in Aspidiiim (Fig. 230, A) it is kidney-shaped, 
in Aspleninm elongated, and free only along one side. Where, 
as in Onoclea (Fig. 230, B), the margins of the sporophyll are 
involute, so as to completely enclose the sori, the indusium is 
wanting or very rudimentary. 



CHAPTER XI 

LEPTOSPORANGIAT^ HETEROSPORE^ (HYDROPTERIDES)' 

The two very distinct families of heterosporous Leptospo- 
rangiatae have obviously but little to do with each other, but, 
both of them being evidently related to the homosporous forms, 
they may be placed together for convenience. Each of the two 
families contains two genera, which in the Marsiliacese are 
closely allied, but in the Salviniacese not so evidently so, 
although possessing many points in common. They are all 
aquatic or amphibious plants, and the gametophyte, especially 
in the Marsiliacese, is extremely reduced. 

Salviniace^ 

The two genera, Salvinia and Azolla, contain a number of 
small floating aquatics which differ very much in the habit of 
the sporophyte from any of the other Filicinese, but in the de- 
velopment of the sporangia and the early growth and form of 
the leaves show aflinities with the lower homosporous Lepto- 
sporangiatse, from some of which they are probably derived. 

The fully-developed sporophyte is dorsiventral, and the 
leaves are arranged in two dorsal rows in Azolla, four dorsal 
and two ventral in Salvinia. The dorsal leaves are broad and 
overlap, so that they quite conceal the stem. Roots are devel- 
oped in Azolla, but are quite wanting in Salvinia, where they 
are replaced physiologically by the dissected ventral leaves 
(Fig. 233). The sporophyte branches extensively, and these 
lateral shoots readily separate, and in this way the plants multi- 
ply with extraordinary rapidity. The sporangia are enclosed 
in a globular or oval "sporocarp," which is really an indusium, 

* Also known as Rhizocarpeae. 

396 



XI 



LEPTOSPORANGIATJE HETEROSPOREM 



397 







v^•'^il'f,t,.% 1 



^ 



''(\ 



"•"'iG. 233. — Salvinia natans. A, Small plant, X2, seen from above; B, a similar one 
from below; w, root-like submerged leaf; C, fragment of a fruiting plant, X2; sp, 
sporocarps; D, a macrosporangial (ma) and microsporangial (mt) sporocarp in longi- 
tudinal section (slightly magnified) ; E, male prothallium with the single anther- 
idium (an) from the side, Xiooo; F, a similar one seen from above; G. sperrna- 
tozoid (Figs. C, D after Luerssen). 



398 MOSSES AND FERNS chap. 

much like that of some of the Hymenophyllacese and Cyathe- 
aceae. 

The Gametophyte 

The first account of the development of the sexual stage 
of the Salviniacese that is in the least degree accurate is Hof- 
meister's ( i), who made out some of the most important points 
in the development of the female prothallium. Pringsheim's 
(i) classic memoir on Salvinia added still more, as well as 
Prantl (4) and Arcangeli ( i ) , but none of these observers were 
able to follow accurately the earliest divisions in the germinat- 
ing macrospores. Berggren's (2) account is the only one on 
the female prothallium of Azolla, except a paper by the writer, 
but Belajeff (4) has given an excellent account of the germina- 
tion of the microspores. 

The Male Prothallium 

The microspores at maturity are embedded firmly in a mass 
of hardened protoplasm, which in Salvinia fills the whole spo- 
rangium, but in Azolla is divided into separate masses, "massu- 
Ige." The wall of the sporangium in Azolla decays and sets these 
free in the water, but in Salvinia the wall of the sporangium is 
still evident when the germination takes place. In the latter the 
young prothallium grows into a short tube, whose basal part is 
separated as a large vegetative cell, from whose base later, Bela- 
jeff states, a small cell is cut off. The upper cell becomes the 
antheridium. In it is first formed in most cases an oblique 
wall, which Belajeff states is always followed by another similar 
one, which forms a central sterile cell separating the two groups 
of sperm cells. This cell, however, did not occur in the speci- 
mens studied by me, where the two groups of sperm cells were 
usually in immediate contact (Fig. 233, E). From each of the 
upper cells peripheral cells are cut off, but they do not com- 
pletely enclose the sperm cells, which are in contact with the 
outer wall of the antheridium. A cover cell corresponding to 
that in the ordinary Fern antheridium is more or less conspicu- 
ous. Each of the central cells divides by cross-walls into four, 
and there are thus eight sperm cells in the ripe antheridium. 
The spermatozoids of Salvinia have about two complete coils. 



XI 



LEPTOSPORANGIATAi HETEROSPORE^ 



399 



and a smaller number of cilia than is usually the case in the 
Filicinese (Fig. 233, G). 

In Acolla the contents of the un^erminated microspore, 
whose wall is thin and smooth, contain but httle granular mat- 
ter. The first indication of germination is the rupturing of 
the exospore along the three radiating ventral ridges, and the 
protrusion of a small papilla. This is cut off by a transverse 
wall near the top of the spore cavity, and forms at once the 
mother cell of the single antheridium (Fig. 234, C). Belajeff 




Fig. 234. — Asolla filiculoides. A, Massula with enclosed microspores (sp), X250; gL 
glochidia; B-D, development of male prothallium and antheridium, X560; o, oper- 
 cular cell; E, cross-sections of a ripe antheridium, X750; i, the top; 2, nearly 
median section; x, second prothallial cell. 



((3)5 P- 329) says the next divisions are nearly parallel and 
divide the antheridium into three cells, one above the other, and 
of these only the middle ones divide further. For some reason, 
which is not quite clear from his account, Belajeff does not re- 
gard the whole upper cell as an antheridium, but says that the 
latter is only formed after five vegetative cells have been cut off. 
Tt seems much more in accordance with the structure found 
in the related homosporous Ferns to regard the whole 



400 MOSSES AND FERNS chap. 

Upper part of the prothallium as the antheridium. In spite of 
his statement that the development of the male prothallium has 
little in common with the true Filices, his figures of Alalia are 
extraordinarily like the simple male prothallia that sometimes 
occur among the Polypodiacese. 

In my earlier studies of the male gametophyte, the second 
prothallial cell (Fig. 234, x), described by Belajeff, was over- 
looked, but subsequent examination of my preparations showed 
that it was present. 

The subsequent divisions correspond to Belajeff's account. 
In the middle cell of the antheridium two nearly vertical walls 
are formed, which with the top cell (cover cell) completely 
enclose the central one. The cover cell recalls in form and 
position the same cell in the antheridium of the Polypodiacese, 
but is formed here previous to the separation of the central cell. 
In one of the lateral cells a horizontal wall is formed, so that 
the sperm cells are surrounded by five parietal ones. The cen- 
tral cell now divides by a median vertical wall, and each of the 
daughter cells twice more, so that eight sperm cells are formed, 
as in Salvinia. The prothallium remains embedded in the sub- 
stance of the massula, and the spermatozoids probably escape 
by the softening of the outer part of the latter. In Salvinia 
the prothallia project beyond the sporangium wall, and are 
easilv detached. 

The antheridium of the Salviniacese does not closely re- 
semble that of any other group. Azolla differs less from the 
homosporous Ferns in this particular, and shows some resem- 
blance to the Hymenophyllacese in the arrangement of the 
parietal cells. Occasionally a triangular opercular cell occurs 
in Azolla, which recalls that in Osmunda. 

The Female Prothallium 

The macrospores of Azolla Uliculoides are borne singly in 
the sporangia. The spores only germinate after they have 
been set free by the decay of the indusium, the upper part of 
which, however, persists as a sort of cap. The decay of the 
sporangium wall and indusium exposes the curious tuberculate 
epispore, with its filam.entous appendages, which serve to hold 
the massulge, which are firmly anchored to them by their 
peculiar hairs (glochidia) with their hooked tips. This is evi- 



XI LEPTOSPORANGIATJE HETEROSPOREM 401 

dently of advantage in bringing the male and female plants 
together. 

The macrospores germinate most promptly in the early 
autumn, and in California, where this species is abundant, this 
is probably the natural time for germination. As the first 
stages of germination take place withir^ the completely closed 
spore, it is difficult to tell precisely just when it begins. So 
nearly as could be determined, the first division may take place 
within two or three days, and the whole development be com- 
pleted within a w^eek. 

A section of the ripe spore, still within the sporangium, 
shows its contents to be nearly uniform, and much like that of 
Isoetes. The nucleus is here at the apex of the spore cavity 
and not conspicuous. It is somewhat elongated and stains but 
little. No nucleolus can be seen. 

The first sign of germination is an increase in the size of 
the nucleus, which becomes nearly globular, and a small nucle- 
olus becomes evident. At the same time the cytoplasm about 
it becomes free from large granules and indicates the position 
of the mother cell of the prothallium. This upper part of the 
spore cavity is now cut off by a nearly straight transverse wall, 
and this small lenticular cell becomes the prothallium. The 
granules in its cytoplasm are finer than those in the large basal 
cell, and the nucleus stains strongly and shows a large nucleolus. 
The nucleus of the lower cell remains in the upper part, and is 
much like that of the prothallial cell. 

The first division wall in the upper cell is vertical and di- 
vides it into two cells of unequal size. In a prothallium having 
but three cells, the second wall was also vertical, but in others it 
looked as if it were horizontal, which Prantl ((4), p. 427) 
states is the case in Salvinia. From the upper of the cells 
formed by the first horizontal wall the first archegonium arises. 
If the horizontal wall forms early, the primary archegonium is 
nealy central, but if two vertical W'alls precede it, its position is 
nearer the side opposite the first cell cut off. In the few cases 
where successful cross-sections of the very young prothallium 
were made, the archegonium mother cell was decidedly tri- 
angular, showing that it was formed by three intersecting walls, 
as in Isoetes. It divides into an outer and inner cell, the latter, 
as in Isoetes, giving rise at once to ^gg and canal cells, wdth- 

out the formation of a basal cell. 
26 



402 



MOSSES AND FERNS 



CHAP. 



Up to this point the exospore remains intact; the central 
cell of the archegonium is only separated from the spore cavity 
by a single layer of cells, and the young prothallium agrees 
closely with Prantl's account of the similar stage of Salvinia 
(Fig. 235, A, B). Berggren's figures of A, Caroliniana, at a 
stage presumably the same, are too diagrammatic to allow of a 
satisfactory comparison. 

Shortly after the first division in the archegonium a rapid 
increase takes place in the size of all the cells of the prothal- 
lium, by which it expands and ruptures the exospore, which 
breaks open by three lobes at the top. 




d-T* 





Fig. 235. — Azolla Uliculoides. A, Luiigituamal section through the upper part of the 
germinating macrospore, X220; h, b, the basal wall of the prothallium; ar, young 
archegonium; n, free nuclei; B, similar section of a nearly developed female pro- 
thallium, X220; C, D, archegonia, X375; h, neck canal cell; v, ventral canal cell; 
o, egg; E, two transverse sections. of a prothallium with the three first archegonia, 
X160; F, median section of a macrospore with large prothallium (pr), X65; in, 
indusium; sp, remains of sporangium wall; ep, perinium. 

The most remarkable difTerence between Azolla and the 
other Hydropterides is the further development of the lower 
of the two primary nuclei.^ In Azolla it undergoes repeated 
divisions, and the resulting nuclei remain embedded in the 
protoplasm in close proximity to the lower cells of the pro- 



^ Recently Coker (i) has observed a fragmentation of the nucleus in 
Marsilia. 



XI LEPTOSPORANGIAT^ HETEROSPOREJE 403 

thallium (Fig. 235, A). This nucleated protoplasm is free 
from the large albuminous granules in the lower part of the 
spore cavity, and in stained sections presents a finely granular 
appearance, and is evidently concerned with the elaboration of 
the reserve food materials in the large spore cavity. In ex- 
ceptional cases indications of the formation of cell walls be- 
tween these nuclei were seen, but usually they remained fjuite 
free. Whether a similar state of affairs exists in Salvinia re- 
mains to be seen. 

When the first archegonium is ripe, the prothallium is nearly 
hemispherical, wath the originally convex base strongly concave. 
The central cell of the archegonium is separated by one, some- 
times two, layers of cells from the spore cavity, and the neck 
projects considerably above the surface of the prothallium. 
The latter now pushes up between the softened episporic mass 
at the top of the spore, and the archegonium is exposed. In 
cross-section the prothallium is more or less triangular (Fig. 
235, E), with one angle longer than the others. This longer 
arm corresponds to the "sterile third" of the prothallium of 
Salvinia, and represents the first cell cut off from the prothallium 
mother cell. 

If the first archegonium is fertilised, no others are formed ; 
but usually several secondary ones are present. The second 
archegonium arises close to the primary one; indeed its cen- 
tral cell is generally separated from it only by a single layer of 
cells. The third arises near the base of the larger lobe (Fig. 
235, E). In case all of these prove abortive, others develop 
between them apparently in no definite order, and to the num- 
ber of ten or occasionally more. In the older prothallia these 
later archegonia are sometimes borne in small groups upon ele- 
vations between the older ones. 

The neck canal cell of the archegonium is formed much 
earlier than Pringsheim describes in Salvinia, and is cut off 
from the central cell about the time the first divisions take 
place in the cover cell. Each row of the neck has four cells, 
as in Salvinia, and the neck canal cell mav have its nucleus 
divide, as in Isoctes and the homosporous Filicineae. This has 
not yet been observed in Salvinia. 

In Salvinia (Pringsheim (i), Prantl (4)) the prothallium 
is large and develops a good deal of chlorophyll. It has a very 
characteristic appearance, and shows the same triangular form 



404 



MOSSES AND FERNS 



CHAP. 



that AzoUa does, but from two of the corners long wing-like 
appendages hang down, and the whole prothallium is saddle- 
shaped. The side joining the two wings is the front, and the 
primary archegonium occupies the highest point, as in Azolla, 

f r c. 




Fig. z^S.—Asolla -filiculoides. Development of the embryo, X350. A, B, C, Young 
embryos in median longitudinal section; D, two horizontal sections of a young 
embryo; E, three transverse sections of a somewhat older one; x, x' , initial cells 
of the cotyledon; F, two longitudinal sections of an advanced embryo; G, hori- 
zontal section of an older one, with the rudiments of the second and third leaves; 
h, b, basal wall of the embryo; st, stem; L^, cotyledon; r, root; h, hairs; x, apical 
cell of the stem; L^, L^, second and third leaves. 

and the two secondary ones form a line with it parallel to the 
forward edge, which develops a meristem and other archegonia 
in rows parallel to the first ones, in case these fail to be fer- 
tilised. 

In Azolla the prothallium has but little power of independ- 



XI LEPTOSPORANGIATJE HETEROSPOREAL 405 

ent existence, and even when unfertilised develops but little 
chlorophyll. No rhizoids occur (this seems to be true of Sal- 
vinia also), and the grov^th only proceeds until the materials 
in the spore are exhausted. To judj^e from Berggren's figures 
A. Caroliniana has a larger prothallium but fewer archegonia 
than A. Uliciiloides. 

The Embryo 

The fertilised ovum, previous to its first division, elongates 
vertically. The basal wall is usually transverse instead of 
longitudinal, as in the other Leptosporangiates, although in 
exceptional cases it may approach this position in Azolla. 
From the epibasal half in the latter arise, as in the other Lep- 
tosporangiatse, the cotyledon and stem apex ; from the hypo- 
basal, foot and root. The quadrant w^alls do not always arise 
simultaneously, but as soon as they are formed the primary 
organs of the embryo are established and are arranged in the 
same way as in other Ferns. Berggren asserts that the root 
does not develop until later, and is derived from the foot ; but 
in sections it is very evident from the first, and corresponds in 
position exactly with that of other Leptosporangiates. 

In all but the stem quadrant the octant walls are exactly 
median, and this may be true of the latter; but in the stem 
quadrant the octant wall may make an acute angle with the 
quadrant wall, and the larger of the two cells then forms at 
once the two-sided apical cell of the stem, and from now on 
divides alternately right and left. Where the octant wall is 
median, it is probable, although this could not be positively 
proved, that the stem apex forms for a short time three sets of 
segments instead of two. 

In the cotyledon the median octant wall is followed by a 
vertical wall in each octant, forming two cells that appear re- 
spectively triangular and four-sided. The former have larger 
nuclei and divide for a time after the manner of two-sided 
apical cells, and perhaps the first division of the leaf quadrant 
may be of the nature of a true dichotomy, and these cells are 
the apical cells of the two lobes. In the four-sided cell, the 
radial and tangential divisions succeed each other with much 
regularity. By the growth of the two initials (Fig. 236, E, 
X, x') the young cotyledon rapidly grows at its lateral margins 



4o6 MOSSES AND FERNS chap. 

and bends forward so as to enclose the stem apex. At the 
same time the upper marginal cells divide rapidly by oblique 
walls alternately on the inner and outer sides, so that the coty- 
ledon also increases in length, and by this time it is about four 
cells thick. 

As soon as the apical cell of the stem is established, it grows 
very much as in the mature sporophyte. Each segment divides 
into a ventral and dorsal half, and each of these into an acro- 
scopic and basiscopic portion. In case the stem octants are 
equal at first it is not possible to say which is to form the stem 
apex, but this is determined by the first division in each cell. 
One of them divides by a vertical wall into equal parts and be- 
comes the second leaf ; the other forms the stem apex. If the 
octants are unequal, the smaller one always forms the leaf. At 
the base of the cotyledon, between it and the stem, is a group of 
short hairs (Fig. 236, F, h). 

The primary root of Azolla arises in exactly the same way 
as that of the typical homosporous Leptosporangiatae, except 
that here the two root octants seem to be always equal in size, 
and as practically only one of them forms the root, the other 
dividing irregularly and becoming merged in the foot, the root 
is more or less decidedly lateral (Fig. 236, E). After one 
complete set of lateral segments has been formed, the primary 
cap segment is cut off from the outer face, but, unlike the other 
Ferns, this is the only one formed. The cap cell divides later 
by periclinal walls, so that there are two layers of cells covering 
the apical cell, and these are continuous with the epidermis of 
the rest of the embryo, and continue to grow at the base, so that 
a two-layered sheath is formed about the young root. The 
lateral segments are shallow and arranged very symmetrically, 
and the divisions correspond to those in the other Ferns. 

The divisions in the foot are more regular than is usually 
the case, and this is especially noticeable in sections cut parallel 
to the quadrant wall (Fig. 236, E). The general arrange- 
ment of the cells is quite like that of the cotyledon, but the 
divisions are fewer and the cells larger. Corresponding to 
the upward grow^th of the cotyledon, the foot elongates down- 
wards beyond the base of the root, which thus appears as a 
lateral growth from it, and no doubt led to Berggren's mistake 
concerning its origin. 

Salvinia in its early stages is much like Azolla, but, accord- 



XI 



LEPTOSPORANGIAT^ HETEROSPORE^ 



407 



ing to Leitgeb/ the apical cell of the stem is always three-sided 
at first, and only later attains its permanent form. The root 
remains undeveloped, and no later ones are produced, but the 
first divisions in what corresponds to the root quadrant in 
Azolla are apparently very similar to those of that plant, and it 
would perhaps be more correct to say that the primary root 
remains undeveloped rather than to consider it as completely 
absent (Dutailly (i)). 

The second leaf in the embryo of Azolla arises practically 
from the first segment of the stem apex, and each subsequent 
segment also produces a leaf. The early growth in length of 



B 





Fig. 237. — Azolla Ulicidoides. Nearly median section of the young sporophyte after it 
has broken through the prothallium, Xioo; B, an older plant with the macrospore 
(sp) still attached; m, massulae attached to the base of the macros^pore; r, the 
primary root, X40. 



the primary root is slow, and it does not become conspicuous 
until a late stage. The vascular bundles are poorly developed 
and arise relatively late. No trace of them can be seen until 
the second leaf is w^ell advanced. Their origin and develop- 
ment correspond to those in other forms described. The 
tracheary tissue is composed entirely of small spiral tracheids. 
The second root arises close to the base of the second leaf, 
and like all the later ones is of superficial origin. As the coty- 
ledon grows, large intercellular spaces form in it, and the young 

'Leitgeb, see Schenk's "Handbuch der Botanik," vol. i. p. 216. 



4o8 



MOSSES AND FERNS 



CHAP. 



sporophyte breaks away from the spore or carries the latter 
with it to the surface of the water. As the embryo breaks 
though the episporic appendages at the top of the spore, these 
are forced apart and the cap-shaped summit of the indusium is 
thrown off. The cotyledon is funnel-shaped, with a cleft on 
one side, and completely surrounds the stem apex. The root 
is still inconspicuous, and forms only a slight protuberance 
upon one side of the foot, which looks like a short cylindrical 
stalk (Fig. 237). 




Fig. 238. — Salvinia natans. A, Horizontal section of the stem apex, X450; L, young 
leaf; B, a young leaf, showing the apical cell {x), X4S0; C, longitudinal section 
of a segment of a ventral leaf, X450; D, section of a dorsal leaf; i, lacunae; h, 
hair, X225; E, cross-section of the stem, Xso-; F, the vascular bundle, X225. 



The growth of the first root is limited, and it differs from 
the later ones by forming peculiar stiff root-hairs. The later 
roots, except the second, do not seem to bear any definite rela- 
tion to the succeeding leaves. 

A careful examination of the ripe macrosporangium shows 
a number of colourless small round bodies occupying the space 



XI LEPTOSPORANGIAT^ HETEROSPORE^ 409 

between its upper wall and the indusiuni. These are the rest- 
ing cells of a Nostoc-like alga — Anahcena Azollcc, — which is 
always found associated with this plant. At the same time 
that the embryo begins to develop, these cells become active, as- 
sume the characteristic blue-green colour of the growing plant, 
and divide into short filaments that at first look like short Oscil- 
laricc. The cells soon become rounded, and heterocysts are 
formed. Some of these filaments remain entangled about the 
stem apex of the embryo, while others creep into special cav- 
ities which are found in all the leaves except the cotyledon, and 
here develop into a colony. 

The first branch is formed after the plant has developed 
about eight leaves, but whether its position is constant was not 
determined 

The Mature Sporophyte 

Strasburger (6) has investigated very completely the tissues 
of the mature sporophyte of Azolla, and Pringsheim ( i ) has 
done the same in Salvinia, so that these points are very satis- 
factorily understood. 

The growing point of the stem in Azolla (Fig. 240, A) is 
curved upward and backward, in Salvinia (Fig. 238, A) it is 
nearly horizontal. In both genera there is a tw^o-sided apical 
cell from which segments arise right and left. Each segment 
divides into a dorsal and ventral cell, and a transverse section 
just back of the apex shows four cells arranged like quadrants 
of a circle. In Azolla the dorsal cells develop the leaves, the 
ventral ones the branches and roots. Each semi-segment is 
divided into an acroscopic and basiscopic cell, and these are fur- 
ther divided into a dorsal and lateral cell in the upper ones, into 
a ventral and lateral one in the lower. The leaves arise from 
one of the dorsal cells, which may be either acroscopic or basi- 
scopic, but is always constant on the same side of the shoot, so 
that the two rows of leaves alternate. The lateral buds, which 
do not seem to appear at definite intervals, arise from one of the 
upper cells of the ventral segment, and alternate with the leaves 
on the same side of the stem. 

The mother cell of a leaf is distinguished by its size and 
position (Fig. 240, B, III, L), and the first division wall, as in 
the cotyledon, divides it into two nearly equal lobes. No trace 



[10 



MOSSES AND FERNS 



CHAP. 



of an apical cell can be found in the young leaf, and in this 
respect, as well as the secondary divisions of the stem segments, 
Azolla differs from Sahinia, where for a long time the young 
leaves grow, as in most Ferns, by a two-sided apical cell (Fig. 
238, B) . Each leaf lobe in A.'jolla is divided into an inner small 
cell and an outer larger one, and the latter is then divided by a 
radial wall. This formation of alternating tangential and 
radial walls is repeated with great regularity, and can be traced 




Fig. 239. — Asolla iiliculoides. A, Longitudinal section of a dorsal lobe of the leaf, X 
about 40; n, cavity with colony of Anabcena; h, unicellular hairs; B, epidermis 
with stomata, X150 (after Strasburger) ; C, longitudinal section of young root, 
X225; sh, root-sheath. 



for a long time. It is not unlike the arrangement of cells fig- 
ured by Prantl ( ( i ) , PI. I, Figs. 2, 3) in some of the Hymeno- 
phyllacese. 

The fully-developed leaves of Asolla are all alike. In A. 
iiliculoides the two lobes are of nearly equal size, the lower or 
ventral one, which is submersed, somewhat larger, but simpler 
in structure. The dorsal lobe shows a large cavity near its base 
(Fig. 239, A), which opens on the inner side by a small pore. 
On the outer side the epidermal cells are produced into short 



XI LEPTOSPORANGIAT^ HETEROSPORE^ 411 

papillate hairs, which in some species, c. g., A. CaroUniana, are 
two-celled. Stomata of peculiar form (Fig. 239, B) occur on 
both outer and inner surfaces. The bulk of the leaf is com- 
posed of a sort of palisade parenchyma, and the cavity is partly 
encircled by an extremely rudimentary vascular bundle. The 
ventral lobe of the leaf is but one cell thick, except in the middle, 
where there is a line of lacunar mesophyll, traversed by a 
simple vascular bundle. 

In Salvinia the leaves are of two kinds. THe dorsal ones 
are undivided, and traversed by a single vascular bundle. The 
mature leaf shows two layers of large air-chambers, separated 
only by a single layer of cells, whose walls are like those of the 
epidermis. From both upper and lower surfaces, but especially 
the former, numerous hairs develop. The ventral leaves are re- 
peatedly divided, and each segment grows by a definite apical 
cell ; the segments are long and root-like, and covered with 
numerous long delicate hairs, looking like rhizoids. These sub- 
mersed leaves doubtless replace the roots. The leaves in Sal- 
vinia are arranged in alternating wdiorls of three, correspond- 
ing to the nodes, and this arrangement accounts for the six rows 
of leaves previously referred to. 

The mature stem shows a central concentric vascular bundle 
(Fig. 238, E, F), whose tracheary tissue is somewhat more 
compact and the tracheae in Azolla than in Salvinia. This is 
surrrounded by a definite endodermis and one or two layers of 
larger parenchyma cells, and radiating from the latter are plates 
of cells separated by large air-spaces, and connecting the central 
tissue with the epidermis (Fig. 238, E). 

The lateral branches arise in acropetal order, but apparently 
not always at equal intervals. Their development is a repetition 
of that of the main axis. Like the branches, the roots in Azolla 
arise acropetally, and their number is very much less than the 
leaves. They arise from superficial cells and follow exactly ia 
their development the primary root of the embryo. The inner 
layer of cells of the sheath, however, in these later roots be- 
comes disorganised, and there is a space between this and the 
root itself. A single root-cap segment only is formed subse- 
quent to the primary one from which the sheath forms, and this 
secondary cap segment undergoes division but once by periclinal 
walls (Fig. 239, C). 

Leavitt (i) found in the older roots of both A. iiliciiloides 



412 MOSSES AND FERNS chap. 

and A. CaroUniana numerous root-hairs, which arise from defi- 
nite cells, evident while the "epiblema" or superficial layer of the 
root is still actively dividing — a condition which also occurs 
in many other Pteridophytes. ^'The initials for these root-hairs 
arise within a belt of actively dividing cells lying immediately 

under the inner root-cap, not far from the apex, As 

the root reaches the limit of its development, the hair-forming 
impulse travels downward until the apical cell itself is split into 
several parts, each one piliferous." (1. c, p. 416, 417.) 

The Sporangia 

The sporangia in both genera are contained in a so-called 
sporocarp, which is really a highly-developed indusium. These 
sporocarps always arise as outgrowths of the leaves, in Salvinia 
from the submersed leaves, in Asolla from the ventral lobes. In 
Salvinia several are formed together (Fig. 233, C), in Azolla 
two, except in A. Nilotica, where there are four. Each sporo- 
carp represents the indusiate sorus of a homosporous Fern. 

In Azolla Uliculoides these sori arise, as Strasburger ((6), 
p. 52) showed, from the ventral lobe of the lowest leaf of a 
branch. My own observations in regard to the origin differ 
slightly from Strasburger's in one respect. Instead of only a 
portion of the ventral lobe going to form the sori, the whole 
lobe is devoted to the formation of these, and the involucre 
which surrounds them is the reduced dorsal lobe of the leaf, and 
not part of the ventral one. 

The leaf lobe, as soon as its first median division is complete, 
at once begins to form the sporocarps, each half becoming trans- 
ferred directly into its initial cell. In this, walls are formed, 
cutting off three series of segments (Fig. 240, D). Next a 
ring-shaped projection arises about it, and this is the beginning 
of the indusium {id) or sporocarp, which bears exactly the 
same relation to the young sorus that it does in Trichomanes, 
and Salvinia shows the same thing. From this point the two 
sorts of sporocarps in Azolla differ. In the macrosporic ones 
the apical cell develops directly into the single sporangium; in 
the microsporangial sorus the apex of the receptacle, which prob- 
ably represents an abortive macrosporangium (Goebel (22), p. 
669) forms a columella from whose base the microsporangia 
develop. (Fig. 241, A.) 



XI 



LEPTOSPORANGIATJE HETEROSPOREJE 



413 







Fig. 240. — Azolla Uliculoides. A, Vertical longitudinal section of the stem apex, X600; 
r, mother cell of a root; B, three successive transverse sections just back of the 
apex; tn, the median wall; L, mother cell of a leaf, X600; C, single lobe of a 
young sterile leaf, X600; D, fertile leaf segments with two very young sporocarp 
rudiments, X6oc; E, longitudinal section of young macrosporangium, showing the 
young indusium {id), X600; t, first tapetal cell; F, older macrosporangium com- 
pletely surrounded by the indusium, X350; n, Anabcena filaments. 



414 * MOSSES AND FERNS chap. 

The development of the sporangium follows closely that of 
the other Leptosporangiatse up to the final development of the 
spores. The tapetum is composed of but a single layer of cells 
in Azolla, but in Salvinia it usually becomes double (Juranyi 
( I ) ) . In both genera the wall remains single-layered, and no 
trace of an annulus can be detected. 

In the macrosporangium of Azolla the archesporium pro- 
duces eight sporogenous cells, the microsporangium sixteen. 
In Salvinia, according to Juranyi, both sporangia contain six- 
teen spore mother cells. ^ Shortly after the divisions are com- 
pleted in the central cell and tapetum the cell walls of the latter 
are dissolved, but for a time the sporogenous cells remain to- 
gether. Finally, they become isolated and round off before the 
final division into the young spores takes place. In the macro- 
sporangium only one spore finally develops. This is at first, 
in Azolla, a thin-walled oval cell lying free in the enlarged cavity 
of the sporangium. Examination shows it to be surrounded by 
a thick layer of densely granular nucleated protoplasm derived 
from the tapetum. As the spore grows the surrounding proto- 
plasm and the abortive spores are used by it as it develops, and 
through their agency the curious episporic appendages of the 
ripe spore are deposited upon the outside. The spore itself is 
perfectly globular and surrounded by a firm yellowish exospore, 
which in section is almost perfectly homogeneous. The epi- 
spore covering this shows over most of the spore a series of 
thick cylindrical papillae, from the top of which numerous fine 
thread-like filaments extend. In section the epispore shows two 
distinct parts, a central spongy-looking mass and an outer more 
homogeneous part covering all but the tops of the papillae. At 
the top of the spore are three episporic masses, composed entirely 
of the spongy substance and surrounding a central conical mass 
from whose summit extend numerous fine filaments like those 
growing from the rest of the epispore. The name ''swimming 
apparatus," which has been applied to this apical mass, is a mis- 
nomer, as the ripe sporangium sinks promptly when freed from 
the plant. 

The indusium rapidly grows above the young macrospo- 
rangium, or group of miscrosporangia, and its walls, which be- 
come double, converge at the top and finally the opening is com- 

^ Heinricher (2), however, states that in the macrospangium there are 
but eight, as in Azolla. 



XI 



LEPTOSPORANGIAT^ HETEROSPORE^ 



415 



pletely closed. In the former, before this happens, filaments of 
Anabccna creep in and enter the resting condition. Thus they 
remain until growth is resumed with the germination of the 
spore, when the embryo is infected. The upper cells of the 
indusium become very dark-coloured and hard, and remain after 
the lower part decays. The wall of the macrosporangium does 



B. 





Fig. 241. — A, Young microsporangial sorus of A^ filiculoides, X80; col, columella; id, 
indusium; B, nearly ripe microsporangium, X22S. 



not become absorbed, as Strasburger ((6), p. 71) states, but 
remains intact, though very much compressed, until the spore 
is ripe. 

The sporocarps of Sahinia are like those of AzoUa, but the 
twQ layers of cells are separated b}^ a series of longitudinal air- 
spaces which correspond to ridges upon the surface of the sporo- 
carp (Fig. 233, D). 

The microsporangia of AzoUa have a long stalk, which is 
composed of usually two, but sometimes three rows of cells. 
The sixteen sporogenous cells all develop, so that there are 
normally sixty-four microspores in each sporangium. These 
have the exospore thin and smooth, and are included in a kind 
of common epispore, w^hich here too owes its origin mainly to 
the tapetal cells. This episporic substance is divided into 
masses (massul^e), which have the foamy structure of the 
episporic apendages of the macrospore. This appearance is 
apparently due to the formation of vacuoles, which make these 



4i6 



MOSSES AND FERNS 



CHAP. 




B. 




Mi 



S^. 



Fig. 242. — Azolla Uliculoides. A, Mature sporophyte, X2; B, lower surface of a branch 
with two microsporangial sori {sp), X6; C, macrosporangial {ma) and microspo- 
rangial {mi) sori, Xio. 



XI 



LEPTOSPORANGIAT^ HETEROSPORE^ 



417 



massulse look as if composed of cells. The tapetal nuclei are 
confined to the outside of the massulae, and can be detected al- 
most up to the time they arc fully developed. Finally, upon 
the outside of the massulae are formed the curious anchor-like 
"glochidia" (Fig. 234, gl), whose flattened form is due to their 
formation in the narrow spaces between the massulse. 

In Salvinia the microsporangia arise as branches from spo- 
rangiophores which bud out from the columella, so that their 
number much exceeds that of the macrosporangia, or of the 
microsporangia of Azolla, There are no separate massulse, 




Fig. 243. — Marsilia vestvta. A, Fruiting plant of the natural size; sp, sporocarps; B, 
a single sporocarp, X4; C, cross-section of the same, Xs; D, germinating sporo* 
carp, showing the gelatinous ring by which the sori (5) are carried out,X3« 



and in the macrosporangium the epispore is much less developed 
than in Azolla. 

The Marsiliace^ 

The two genera of the Marsiliacese, Marsilia and Pihdaria, 
are much more closely related than Salvinia and Azolla, and at 
the same time their resemblance to the homosporous Ferns is 
27 



4i8 MOSSES AND FERNS chap. 

closer, and of the two genera Pilularia is evidently the nearer 
to the latter. The development of both gametophyte and 
sporophyte in the two corresponds very closely. 

The sporangia are borne in "sporocarps," which are mor- 
phologically very different from those of the Salviniacese, be- 
ing metamorphosed leaf segments enclosing several sori, and 
not single sori enclosed simply in an indusium. The spores 
germinate with extraordinary rapidity, especially in Marsilia, 
and in M. ^gyptiaca the writer has found a two-celled embryo 
developed within thirteen hours from the time the ungermi- 
nated spores were placed in water. 

The sporocarp of Marsilia is a bean-shaped body, which is 
attached to the petiole of the leaf by a more or less prominent 
pedicel. It is very hard, and unless opened artificially may 
remain a long time unchanged,. if placed in w^ater ; but if a little 
of the hard shell is cut away, the swelling of the interior muci- 
laginous tissue quickly forces apart the two halves of the fruit. 
As more water is absorbed, this gelatinous inner tissue con- 
tinues to expand and forms a long w^orm-shaped body (Fig. 
243, D), to which are attached a number of sori, each sur- 
rounded by a sac-shaped indusium in which the sporangia are 
closely packed. Macrosporangia and microsporangia occur in 
the same sorus. The former contain a single large oval white 
spore, the latter much more numerous small globular ones. 
The indusium remains intact for several hours, if not injured, 
but finally, with the sporangium w^all, is completely dissolved, 
and the spores are set free. 

The Microspores and Male Prothallium 

The microspores of M. vestita (Fig. 244) are globular cells 
about .075 mm. in diameter. The outer w^all is colourless and 
sufficiently transparent to allow the contents to be dimly seen. 
Lying close to the wall are numerous distinct starch granules, 
and in the centre the nucleus is vaguely discernible. Sections 
through the ungerminated spore show that the wall is thick, 
with an inner cellulose endospore, outside of which are the 
exospore and the epispore or perinium, composed of closely- 
set prismatic rods. The central nucleus is large and distinct, 
with usually one or two nucleoli. 

The first division takes place at ordinary temperatures, 



XI 



LEPTOSPORANGIATAi HETEROSPOREJE 



419 



about 20° C, within about an hour after the spores are placed 
in water. Previous to this the nucleus enlarges and moves to 
one side of the spore, usually the point opposite the apex, and 
the granular cytoplasm collects near the centre and is connected 
with the peripheral cytoplasmic zone only by thin strands. 
The first wall divides the spore into two very unequal cells, the 




Fig. 244. — Marsilia vestita. Germination of the microspores, X450; x, vegetative pro- 
thallial cell; m, basal antheridial cell; p, peripheral antheridial cells; A, an unger- 
minated spore, ventral aspect; B, section of a similar one — all longitudinal sections 
except E and F, which are transverse. In these the two groups of sperm cells are 
separated by a large sterile cell. 

smaller containing but little granular contents, and representing 
the vegetative part of the prothallium, while the upper becomes 
the antheridium. In Pilularia there is subsequently cut off a 
small cell from the vegetative cell, and Belajeff (4) states that 
this also is always the case in Marsilia, but it is less conspicuous 



420 



MOSSES AND FERNS 



CHAP. 



than in Pilularia (Fig. 245, A, y). The next division is not 
always the same, but is usually effected by a wall nearly parallel 
to the first one, but more or less concave (Fig. 244, D). Some- 
times the antheridial cell divides at once by an oblique wall into 
two nearly equal cells, from each of which a group of sperm 
cells is later cut off. In no case was the central cell cut off by 
a dome-shaped wall, such as is common in the homosporous 
Ferns, and also in Pilularia. The formation of this wall is 
apparently suppressed here, perhaps as the result of the ex- 
tremely rapid development of the antheridium, and the separa- 
tion of the sperm cells takes place by walls cut off from the 
periphery of the two upper cells. A cap cell (Fig. 245, d) is 
almost always present, as in Pilularia and the Polypodiaceae. 

From the two cells of 
the middle part of the 
antheridium a varying 
number of sterile cells are 
cut off, which are quite 
transparent, while the 
contents of the central 
cells are very densely 
granular. Not infrequent- 
ly the two groups of 
sperm cells are completely 
separated by one of these 
sterile cells (Fig. 244, F), 

Fig. 245.—Mars{lia vestita. A, Longitudinal, B, ^^^ Bclajcff COnsidcrS 

transverse division of the male gametophyte, that Cach grOUp of SpCrm 

X400; X, y, the two vegetative prothallial ii rpnrPQPntQ P Hktt'nrt 

cells; C, two free spermatozoids, X8oo; v, ^^^^^ represents a QlStmCt 

vesicle. antheridium. In view of 

the relationship between 
the Marsiliacese and Schizseaceae, indicated by recent studies 
on the structure and development of the two families (Camp- 
bell (26)), this view has some support, as there is a cer- 
tain resemblance between each of these cell groups and the 
simple antheridium of Aneimia or Schizcea. The divisions in 
the central cells are very regular, and the sixteen sperm cells in 
each group are arranged very symmetrically (Fig. 245). The 
whole number in M. vestita is completed in about seven hours 
from the time germination begins, and the formation of the 
spermatozoids commences about an hour later and takes about 




XI LEPTOSPORANGIATAI HETEROSPOREJE 421 

four hours for its completion. Pilularia approaches much nearer 
to the Polypodiacese in the structure of the antheridium (Fig. 
246). The first funnel-shaped wall is much more frequently 
extended to the basal wall, and the two groups of sperm cells 
are much less distinct than in Marsilia. 

The spermatozoids of Marsilia are at once distinguished 
by a great number of coils, sometimes thirteen or fourteen in 
M. vestita. The cilia are very numerous, but are attached only 
to the broad lower coils, the upper narrow ones l^eing quite free 
from them. The vesicle attached to the broad lower coils is 
very conspicuous and contains numerous starch granules as 
well as albuminous ones. In Pilularia the long upper part of 
the spermatozoid is absent, and it apparently corresponds only 
to the few broad basal coils of that of Marsilia, which are of 
nuclear origin, like the 
greater part of the body 
in the spermatozoid of 
Pilularia. 

Shaw (3) and Belajeff 
(7) have studied the de- 
velopment of the sperma- 
tozoid in Marsilia, Shaw's x-- x x-y, y 
studies on M. vestita be- p , ^. ,, . ,. r p, , • , t, ,• 

riG. 246. — Kipe antheridium or rilulana globuh- 
ing especially complete. fera, showing the two vegetative prothallial 

At the close of the sec- ""f'}'' ^^\ ^'^^'' ^: ^51" ^^^^^l'^^^^^' 

showing the large vesicle (v) with the con- 
Ond from the last division tained starch granules. 

of the central tissue of the 

antheridium, there appears at either pole of the spindle a small 
body, the *'blepharoplastoid," w^hich seems later to divide, the 
two halves increasing in size and remaining together near the 
resting nucleus. These two blepharoplastoids seem to disap- 
pear during the early stages of the next mitosis, but shortly 
afterwards there is seen at either pole of the spindle a small 
blepharoplast (b). At the close of the mitosis the blepharo- 
plast lies near the nucleus of the cell (the secondary sperma- 
tocyte of Shaw^) . This blepharoplast divides, and the daughter 
blepharoplasts increase in size, finally occupying a position near 
the poles of the nuclear spindle (Fig. 247, B). This division 
results in the formation of the spermatozoid mother cells, or 
spermatids. 

After the division into the spermatids is complete, the 




422 



MOSSES AND FERNS 



CHAP. 



blepharoplast increases in size, and shows several granular 
bodies within it, and it is from these granules that the cilia- 
bearing band is developed. 

The blepharoplast becomes much elongated and with the 
nucleus moves toward one side of the sperm cell (Fig. 247, D). 
The nucleus also elongates, but the blepharoplast extends far 
beyond it. The blepharoplast finally forms a funnel-shaped 
coil of ten or more turns, of w^hich the three posterior coils, 
which are much wider, are in contact with the slender coiled 
nucleus, which does not extend beyond this point. (Fig. 247, E). 

The Macrospore and Female Prothallium 

The macrospores of the Marsiliaceae are extremely complex 
in structure, and are borne singly in the sporangia. In Mar- 




FlG. 247. — Marsilia vestita. Development of the spermatozoid, X1500. A-C, lasd 
division preliminary to the formation of the spermatids; D-F, development of the 
spermatozoid; n, nucleus of spermatid; b, blepharoplast (after Shaw). 



silia vestita they are ellipsoidal cells about .425X.750 mm. in 
diameter, ivory-white in colour, and covered with a shiny muci- 
laginous coating. The upper part of the spore has a hemi- 
spherical protuberance covered with a brown membrane, and 
it is the protoplasm within this papilla that forms the prothal- 
lium. The apex of the papilla shows the three radiating ridges 
like those in the microspores, and indicates that, like them, the 
macrospore is of the radial or tetrahedral type. 

Sections of the ungerminated spore (Fig. 248, A) show a 
structure much like that of the microspore, but more highly 



XI 



LEPTOSPORANGIATJE HETEROSPOREJE 



423 



developed. A noticeable difference is the segregation of the 
protoplasm containing the nucleus, which occupies the apical 
papilla. This is filled with fine granules, but is entirely free 
from the very large starch grains of the large basal part of the 
spore. The nucleus is somewhat flattened. A similar arrange- 
ment of the spore contents is found in Pihilaria, but the apex 
of the spore does not form a distinct papilla. The epispore is 
of nearly equal thickness, except at the extreme apex, in Mar- 
silia, but in Pilularia, especially in P. glohnUfcra, the epispore 




Fig. 248. — Marsilia vestita. Germination of the macrospore; A, longitudinal section of 
the ripe macrospore, X6o; n, nucleus; B-G, successive stages in the development of 
the female prothallium and archegonium, X360; C, E, transverse sections, the 
others longitudinal; n, neck canal cell; h, ventral canal cell; r, receptive spot of 
the egg; k, remains of the nucleus of the spore cavity. 



of the upper third is much thicker, and from the outside the 
spore appears somewhat constricted below this. 

Previous to the first division, which in M. vestita takes 
place about two hours after the spores are placed in water, the 
amount of protoplasm at the apex increases, and the nucleus 
becomes nearly globular and there is an increase in the amount 
of chromatin. In Pilularia the first wall is always transverse 
and cuts off the mother cell of the prothallium; but in Mar- 
silia, while this is usually so, occasionally a lateral cell is cut 



424 



MOSSES AND FERNS 



CHAP. 




off first from the papilla. In Pilularia the next wall is parallel 
to this transverse primary wall, and this may also occur in 
Marsilia, but in the latter more commonly the first lateral cell 
is first cut off by a vertical wall, and this is followed by two 
others, which intersect it and include a large central cell (Fig. 
248, E), from which a basal cell is subsequently separated. In 
Pilularia, besides the formation of the basal cell by the second 
wall, the central cell is, as a rule, cut out by two, and not three, 
walls. The basal cell of the archegonium in Marsilia divides 

by cross-walls into equal quad- 
rants, and the lateral cells divide 
both by vertical and horizontal 
walls before any further divi- 
sions take place in the arche- 
gonium. This finally divides 
into the cover cell and inner cell. 
The neck is very short, especially 
in Marsilia, and each row has but 
two cells. These in Pilularia 
(Fig. 249) are much longer. 
Both neck and ventral canal cells 
are very small, especially in Mar- 
silia, and the former has its nu- 
cleus undivided.' In Marsilia 
the prothalliiim grows gradually 
as the divisions proceed, but in 
Pilularia (Fig. 249) the young 
prothallium increases but little in 
size until the divisions are almost 
Fig. 249.-Piiuiaria giobuUfera A, B. completed, whcu there is a sud- 

Young female prothalha, longitu- ^ 

dinai section, X300; c, neck canal dcu enlargement. The complete 

cell; C. section of a recently fer- development of the prothallium 

tilised archegonium, X300; sp, / ^ 

spermatozoid within the egg. OCCUpicS about tWClvC tO fifteen 

hours in Marsilia vestita, and in 
Pilularia glob ulif era forty to forty-five hours. 

Coker ( i ) states that in Marsilia Drummondii the nucleus 
in the basal part of the spore subsequently becomes very large 
and irregular in form and finally divides amitotically in several 
parts which apparently remain active for some time. 

The tgg in both genera is large, but in Marsilia it is the 
larger. In both, the receptive spot is evident. The nucleus 




XI 



LEPTOSPORANGIATAL HETEROSPOREJE 



425 



is unusually small in Marsilia, which otherwise resembles 
Pilularia. 

The phenomena of fecundation are very striking in the 
Marsiliacese. The mucilaginous layer al3out the macrospore 
attracts and retains the spermatozoids, which collect by hun- 
dreds about it. The mucilage above the archegonium forms 






1. 




2. 




FiC. 250. — Marsilia vestita. Development of the embryo. A, Longitudinal section of 
archegonium with two-celled embryo; B, similar section of a later stage; C, two 
transverse sections of a young embryo; D, two longitudinal sections of an older 
one; I, I, the basal wall; L, cotyledon; st, stem; r, root; F, foot. A-C, XS25; 
D, X260. 



a deep funnel, which becomes completely filled with the sperma- 
tozoids. As these die their bodies become much stretched out, 
so that they look very different from the active ones, with their 
closely placed coils. The attractive substance here is not con- 
fined to the material sent out from the open archegonium, as the 



426 MOSSES AND FERNS . ^ . chap.^ 

spermatozoids collect in equal numbers about those which are 
still closed, and even about spores that have not germinated 
at all. Marsilia did not prove a good subject for studying the 
behaviour of the spermatozoid within the egg, owing to the 
difficulty of differentiating the spermatozoid after its entrance. 
Pilularia is better in this respect, and shows that the changes 
are the same as those described in Marattia and Osmunda. 

Coincident with the first divisions in the embryo, each of 
the lateral cells of the prothallium (venter) divides by a peri- 
clinal wall, but the basal layer of cells remains but one cell thick. 
The prothallium grows with the embryo for some time, and in 
its later stages develops abundant chlorophyll, and its basal 
superficial cells grow out into colourless rhizoids. In case the 
archegonium is not fertilised, the prothallium grows for a long 
time, and reaches considerable size, but never develops any 
secondary archegonia. In Pihilaria, both prothallium and em- 
bryo may develop chlorophyll in perfect darkness (Arcangeli 
(i),p. 336). 

The Embryo (Hanstein {2) ; Campbell {j, i^)) 

The two genera correspond very closely in the development 
of the embryo, which shows the greatest resemblance to the 
Polypodiaceae. In Marsilia the development of the embryo 
proceeds very rapidly. The first division of the egg is com- 
pleted within about an hour after the spermatozoid enters, and 
in Pilularia after about three hours, as nearly as could be made 
out. In both the basal wall is vertical and divides the some- 
what flattened egg exactly as in Onoclea. The quadrant walls 
next follow, and then the octant wall, as usual. Of the latter 
the one in the root quadrant diverges very strongly from the 
median line (Fig. 250, C), and that in the foot quadrant is 
much like it. In the others it is nearly or quite median, and it 
is impossible to say which of the leaf and stem octants is to 
form the apical cell of those organs. The relative position of 
the young organs is exactly the same, both with reference to 
each other and to the archegonium, as in the Polypodiaceae. 

The Cotyledon 

The cotyledon grows for a time from the regular divisions 
of one or both of the primary octant cells, but this does not 



LEPTOSPORANGIATJE HETEROSPOREJE 



427 



usually continue long, and the subsequent growth is purely 
basal. The cotyledon is alike in both genera, and is a slender 
cylindrical leaf tapering to a fine point, where the cells are much 
elongated and almost colourless. Its growth is at first slow, 
but at a later period (in Pihilaria globidifcra about the eighth 
day) it begins to grow with great rapidity and soon reaches its 
full size. This is largely due to a simple elongation and ex- 
pansion of the cells, which are separated in places, and form a 
series of longitudinal air-channels separated by radiating plates 
of tissue (Fig. 251, i). The simple vascular bundle traversing 




Fig. 251. — Longitudinal section of the young sporophyte of Pilularia glohulifera, still 
enclosed in the calyptra {cal), and attached to the macrospore isp), X75; B, the 
lower part of the same embryo, X21S; r, apical cell of the root; st, apical cell of 
the stem; i, lacunae. 

the axis is concentric, with a definite endodermis, but the 
tracheary tissue is very slightly developed. This becomes first 
visible about the time the leaf breaks through the calyptra. 

The Stem 



Of the two octants in the stem quadrant one becomes at 
once the apical cell of the stem, the other the second leaf, as in 
other Leptosporangiatse. The first wall in each octant meets 
octant and quadrant walls, and cuts off a large cell from each 



428 - MOSSES AND FERNS chap. 

octant, in contact with the foot. Hanstein and ArcangeH re- 
gard these as part of the foot, and physiologically they no doubt 
are to be so considered, but morphologically they are beyond 
question segments respectively of the stem and second leaf. At 
first these are not distinguishable from each other, but the divi-' 
sions in the latter are usually (in Pilularia) less regular, and 
the apical cell early lost. It may, however, develop a regular 
three-sided apical cell, like that of the later leaves. The earlier 
segments of the stem apex are larger than the subsequent onesy 
and the broadly tetrahedral form of the primary octant is re- 
duced to the much narrower form found in the older sporophyte. 

The Root 

The first wall in the root quadrant strikes the basal w^H 
at an angle of about 60°, so that the octants are of very unequap 
size (Fig. 250, C), and the larger one, as in other similar cases, 
becomes at once the initial cell of the root, which in both genera 
shows the same regular divisions that characterise the Poly- 
podiacese. The segments of the root-cap do not form any peri- 
clinal walls, and remain single-layered. The root, like the 
cotyledon, is traversed by regular air-chambers, and its trans- 
verse section resembles very closely that of the leaf. These air- 
chambers appear while the root is very young, and at a point 
between the endodermis and the cortex. The latter is at this 
stage divided into but two cells, the outermost of which by a 
further tangential division becomes two-layered, the outer 
forming the epidermis, and the inner by similar divisions be- 
comes three-layered. The two outer layers divide by radial 
walls, but the inner ones divide only by periclinal walls, and 
form one-layered lamellae separating the air-spaces and connect- 
ing the endodermis with the outer cortex. 

The Foot 

The first divisions in the foot quadrant follow closely those 
in the root, but this regularity soon ceases, and after the first 
divisionis no definite succession in the walls can be distinguished. 
The foot remains small, but, as we have seen, the first segments 
of the lower epibasal octants practically form part of it, and 
doubtless all the lower cells are concerned in the absorption of 



XI LEPTOSPORANGIATJE HETEROSPOREJE 429 

food from the spore. The vokime of tlie protoplasm in the 
spore increases as the prothahium grows, but loses more and 
more its coarsely granular structure. In both Marsilia and 
Pihilaria the nucleus of the spore cavity soon becomes indis- 
tinguishable, and in the former is from the first very small. In 
Pihilaria it is larger, and in the later stages lx)dies vv^ere ob- 
served that looked as if they might be secondary "endosperm- 
nuclei," like those of Azolla, but their nature was doubtful. A 
further study of Marsilia vestita has shown irregular deeply 
staining bodies in the protoplasm below the basal prothallial 
cells, w^hich may perhaps be nuclei like those described by Coker 
(i) in M. Drwmnondii. 

The early leaves are at first alike in both genera, and the 
earliest ones do not show any trace of the circinate vernation of 
the later ones. In Pihilaria the later leaves are essentially like 
the cotyledon, but in Marsilia all the later leaves show a distinct 
lamina. This is at first narrow and undivided, and spatulate 
in form. In M. vestita this is succeeded by five or six similar 
ones, with constantly broadening laminae, w^hich finally divide 
into two narrow wedge-shaped lobes, and these are then suc- 
ceeded by others with broader lobes, which finally are replaced 
by four lobes, the central ones being narrower than the outer 
ones. All of these early lobed leaves are folded flat, and it is 
not until about ten or twelve leaves have been formed that 
finally the leaf attains the form and vernation of the fully-devel- 
oped ones. 

The divisions in the stem apex take place slowly, but appar- 
ently a complete series of segments is produced in rapid succes- 
sion, and there is an interval before any more divisions occur, 
as there is always considerable difference in the ages of any 
two succeeding sets of segments. The apical cell of Pihilaria 
in cross-section has the form of an isosceles triangle with the 
shorter face below. Probably each dorsal segment at first 
gives rise to a leaf, and each ventral one to a root. However, 
the number of roots exceeds that of the leaves, but the origin 
of these secondary roots was not further investigated. 

The Mature Sporophyte 

In both Marsilia and Pihilaria the fully-developed sporo- 
phyte is a creeping slender rhizome, showing distinct nodes and 



430 



MOSSES AND FERNS 



CHAP. 



hi 




Fig. 2$^ — Part of a fruiting plant of Ptlularia Americana, X4; sp, sporocarp^ v' "^i 



XI 



LEPTOSPORANGIATAi HETEROSPOREJE 



431 



internodes. At the nodes are borne the various appendages of 
the stem, and the elongated internodes are, except for occa- 
sional roots, quite destitute of appendages. Leaves and 
branches arise from the nodes, and in Marsilia are much 
crowded. The plants are aquatic or amphibious, and the habit 
of the plant is very different, especially in Marsilia, as it grows 
completely submerged, or partially or entirely out of water. 
Some species, like M. vestita, which grow where there is a 






.H-> 




Fig. 253. — Marsilia vestita. A, Vertical longitudinal section of the stem apex, X8o; 
L, leaves; st, stem apex; r, roots; B, the stem apex, X450; C, horizontal section of 
very young leaf, X450; D, similar section of an older one, X450; E, cross-section 
of petiole, X80. 



marked dry season, grow in shallow ponds or pools, which dry 
up as the end of the growing period approaches, and the ripen- 
ing of the sporocarps takes place after the water has evaporated. 
In the first case the petioles are extremely long and weak, and 
the leaf-segments float upon the surface. In the other case the 
petioles are much shorter and stouter, and the leaves are borne 
upright. The young leaves are circinate, as in the ordinary 
Ferns, and in Pilularia retain the same structure as the coty- 



432 MOSSES AND FERNS chap. 

ledon. In Marsilia they are always four-lobed. The sporo- 
carps are modified outgrowths of the petiole, which are often 
formed so near the base as to appear to grow directly from the 
stem. They often are borne singly, but may occur in consider- 
able numbers — twenty or more in M. polycarpa — and are glob- 
ular in Pilularia, bean-shaped in Marsilia. The growth of the 
stem and the origin of the various appendages are the same in 
both genera. 

A longitudinal section of the stem (Fig. 253, A) shows the 
decidedly pointed apex occupied by a large and deep apical 
cell with very regular segmentation. Each segment divides 
into an inner and an outer cell, the former in all the segments 
forming the central plerome cylinder, and the outer cells devel- 
oping the cortex of the stem, and the leaves in the dorsal seg- 
ments, the roots in the ventral ones. The young leaves are 
separated by distinct intervals or internodes, and apparently 
all of the dorsal segments do not give rise to leaves, but just 
what the relation is between the nodes and internodes was not 
determined. The roots arise in strictly acropetal order from 
the ventral segments, but their number does not seem to be 
constant. In Pilularia Americana the number of roots con- 
siderably exceeds that of the leaves, as it does in the young 
sporophyte of P. glohulifera. 

The single axial vascular bundle is truly cauline, and ex- 
tends considerably beyond the base of the youngest leaf. The 
later leaves in Pilularia, both in their growth and complete 
structure, correspond to the primary ones. They grow for a 
time from a three-sided apical cell, in which respect they differ 
from Marsilia} The development of the leaf of the latter has 
been carefully studied by Hanstein in M. Drummondii, and M. 
vestita corresponds exactly with that species. A section of the 
very young leaf (Fig. 253, C) parallel with the surface shows 
a large two-sided apical cell. The leaf-rudiment assumes a 
somewhat spatulate form, and on either side a projecting lobe 
is formed, the rudiment of one of the lateral segments of the 
leaf. The apical cell is now divided by a median wall, after 
which periclinal walls are formed, and from this time the 
growth of the leaf can no longer be traced to a single initial cell. 
The first longitudinal wall in the apical cell establishes the two 

'^Pilularia glohulifera, according to Johnson (2) and Meunier (i) has 
the typical two-sided cell found in Marsilia. 



XI LEPTOSPORANGIATAL HETEROSPOREJE 433 

terminal lobes, which at first are not separated (Fig. 253, D). 
The establishment of the veins follows exactly as in Ferns with 
a similar venation, and is strictly dichotomous. The stem 
branches freely in both genera, and the branches arise close to 
the apex, and below a young leaf somewhat as in Azolla. 

The roots correspond closely to those of the higher 
homosporous Ferns. The segmentation of the apical cell fol- 
lows the same order as in the PolypodiacCce. Goebel's figure of 
M. salvatrix ( ( 10), p. 238) differs somewhat from the account 
given more recently by Andrews ( i ) for M. qiiadrifoUa. The 
latter observer states that there are no periclinal walls in the 
root-cap segments, which remain throughout one-layered, and 
that the separation of the plerome takes place earlier than Goe- 
bel indicates. Van Tieghem's ((5), p. 535) account of the 
root of M. Dnimmondii confirms Andrews' observations upon 
M. qiiadrifolia. The bundle of the root is diarch, as in the 
Polypodiacese, and the lateral roots arise in the same manner. 
The endodermal cells from which they spring are distinguished 
from the others by their shorter and broader form, and are very 
easily recognisable by this as well as from their position. They 
form two vertical rows exactly opposite the ends of the xylem 
plate, and the lateral roots therefore are also strictly two-ranked. 
Narrow lacunae are formed in the cortical tissue of the root, 
and the cells surrounding these are connected by regular series 
of short outgrowths, which connect them in a way that recalls 
very strongly the connecting tubes between conjugating fila- 
ments of Spirogyra, and produce a similar ladder-like ap- 
pearance. 

The solid vascular cylinder of the young stem is later usu- 
ally replaced by a tubular one, but its structure is also con- 
centric, with phloem completely surrounding the xylem, and it 
has both an inner and outer endodermis. When the plants are 
completely submerged the ground tissue is mainly parenchyma, 
but in the terrestrial forms sclerenchyma may be developed in 
the cortex of the stem and petiole. The latter is always trav- 
ersed by a single axial bundle, which in the lamina in Mazsilia 
divides repeatedly near the base of the wedge-shaoed leaflets 
into numerous dichotomous branches. 

Luerssen ((7), p. 601) mentions as special reproductive 
bodies, tubers found in M. hirsuta. These are irregular side 
branches covered w^ith imperfectly-developed leaves, and with 
28 



434 



MOSSES AND FERNS 



CHAP. 



the cortical tissue strongly developed and full of starch. These 
are supposed to survive long periods of drought, and to germi- 
nate under favourable conditions. A condition somewhat 
analogous to this appears in M. vestita (Fig. 243, A), but 
whether these short lateral branches are of this nature was not 
investigated. 

The Sporocarp (Sachs (i) ; Goehel (6) ; Meunier (i) ; 

{Johnson {i, 2)) 

The development of the sporocarp is much the same in the 



L ^ 







^ . \^i "r^ 




Fig. 254. — Pilularia Americana. Development of the sporocarp. A, Very young 
sporophyll with sporocarp rudiment (sp) , showing a distinct apical cell; B-D, 
longitudinal sections of young stages, showing the formation of the "sorus canals'* 
isc), X130; V, the original apex of the young sporocarp; L, secondary lobes or- 
leaflets; E, longitudinal section of an older stage, X about 130; s, s, young sori; 
F, transverse section of an older sorus, X180. 



two genera, but is most easily followed in the simple sporocarp 
of Pilularia. In P. Americana, the young fruit begins to de- 
velop almost as soon as the leaf can be recognised, and while it 
is still close to the stem apex. Growth is stronger upon the 
back of the young leaf, and it very early assumes the circinate 



XI .j> LEPTOSPORANGIAT^^ HETEROSPORE^ 435 

form. Before this curvature is very pronounced, however, in 
the sporophyll, a protuberance arises upon its inner face, a short 
distance above the base (Fig. 254, A). This originates from a 
single cell, which functions for some time as an apical cell, and 
causes the young sporocarp to project strongly from the leaf, of 
which it is simply a branch, somewhat analogous to the spike in 
Ophioglossuni. It may, perhaps, be better compared to a fertile 
leaf segment of Ancimia, as it has been shown by Johnson (2), 
that the mother cell of the young sporocarp arises from the 
margin and not from the face of the leaf. 

It has at first the form of a blunt cone, but soon upon the 
side turned toward the leaf a slight prominence appears (Fig. 
254, B, L) , and about the same time two similar lateral ones are 
formed. As in the sterile part of the leaf growth is stronger 
on the outside, and the young sporocarp bends in toward the 
leaf, so that the position of fertile and sterile segments is very 
like that in the young sporophyll of Ophioglossuni. The apex 
of the sporocarp rudiment, together with the three lobes, en- 
close a slightly depressed area, which becomes the top of the 
sporocarp. The four prominences (including the original 
apex of the fertile segment) are beyond question to be consid- 
ered leaflets, which remain confluent except at the top. A little 
later a slight depression or pit forms at the base of each lobe 
and the central area at the top. These pits are separated later- 
ally by the coherent edges of the leaflets, which extend to the 
axis of the sporocarp and are continuous with it. As the 
young fruit enlarges, the depressions deepen owing to the 
elongation of both leaflets and the axial tissue, which forms a 
sort of central columella (Fig. 254, D). Thus are formed 
four deep cavities, separated laterally by the united margins of 
the leaflets, and corresponding to the much more numerous 
"canals" described by Russow and Johnson in the fruit of 
Marsilia; like these they at first open at the summit by a pore, 
and a study of longitudinal sections shows clearly their strictly 
external origin. 

From his study of P. glohulifcra, Johnson (2) concludes 
that all four lobes of the sporocarp are of lateral origin. He 
was able to trace the origin of each sorus to a single marginal 
cell in each of the four segments of the young sporocarp. Sec- 
tions of the young sporocarp of Marsilia at this stage (John- 
son (i), Figs. 22, 22^) resemble to an extraordinary degree 



436 



MOSSES AND FERNS 



CHAP. 



the young fertile segment of the leaf of Schizcea, where the 
relation of the sporangia to the leaf margin is very similar. 

Up to the time the cavities begin to form, the young fruit 
is composed of uniform tissue, but shortly after, the tissue sys- 
tems become differentiated, and the peduncle of the sporocarp 
is formed. At this time the vascular bundle of the peduncle 
can be recognised, and joins that of the sterile segment near 




Fig. 255. — Marsilia quadrifolia. A, Horizontal section of very young sporocarp, X500; 
B, transverse section of an older sporocarp; s c, sorus canal; sp, young sporan- 
gium, X about 340; C, horizontal section of young sorus showing the large apical 
macrosporangium, and the lateral microsporangia, mi; in, the indusium. (After 
Johnson.) 



its base. The peduncle is much longer in P. Americana than 
in the very similar P. globulifera. The circinate coiling of 
the sterile segment is repeated, though less conspicuously, here, 
and the body of the sporocarp is bent at right angles to the 
peduncle. 



LEPrOSPORANGIAT^ HETEROSPORE^ 



437 



The cavities rapidly become larger with the expansion of 
the growing sporocarp, but the space between the inner surface 
of the lobes and the columella remains narrow, owing to the 
growth of the sorus, w^hich almost com[)letely fills it from the 
first. The sorus forms an elongated cushion, extending nearly 
the whole distance from the apex to the base of the lobe, along 
the median line of its inner face. In origin and position it 
corresponds closely to that of the Schizseacese. 




Fig. 256. — Transverse section of an older sporocarp of P. Americana, showing the four 
sori is); fb, vascular bundles, X85; B, section of the wall of a nearly ripe sporo- 
carp, X2SS. 



The vascular bundle of the peduncle divides into four 
branches, where it enters the sporocarp, and one branch goes 
to each lobe, of which it forms the midrib lying below the 
sorus. From each of these two smaller branches are given 
off near the base, following the margin of the lobe (Fig. 256, 



438 MOSSES AND FERNS ' chap. 

A). By this time the outer epidermal cells begin to thicken, 
the first indication of the hard shell found in the ripe sporo- 
carp. 

The development of the sporangia corresponds most nearly 
to that of the Schizseaceae. The surface cells of the sorus pro- 
trude as papillse, in which the same divisions arise as in other 
Leptosporangiatse. The first division wall is usually strongly 
oblique, but may. be transverse. The formation of the arche- 
sporium is the same, but the apical growth of the sporangia is 
checked sooner in the earlier ones, which have consequently a 
very short stalk. In the later ones, which arise between the 
others, the stalk is longer. The first sporangia are formed at 
the base of the sorus, and their development proceeds toward 
the apex; but later secondary ones may arise at any point in 
the sorus. 

The tapetum is well developed, and, as in most homospo- 
rous Ferns, consists of two layers, in some places of three. 
The number of sporogenous cells is usually eight, but some or 
all of these may divide again, so that the whole number ranges 
from eight to sixteen. The dissolution of the tapetum walls 
and subsequent division of the spores follow precisely as in 
Azolla. In stained sections the nucleated protoplasm of the 
tapetal cells is very evident after the walls have disappeared. 
At this point the difference in the two kinds of sporangia be- 
comes manifest. Those in the lower part of the sorus, i. e., 
the oldest ones, form the macrosporangia, the upper ones 
microsporangia. In the latter all the spores mature; in the 
former, as in Azolla, one spore grows at the expense of the 
others, and finally fills the sporangium completely. 

It has been generally supposed that no trace of an annulus 
could be detected in the Marsiliaceae. The writer has found, 
however (Campbell (26)), in Pilularia Americana, traces of 
a terminal annulus like that of the Schizseacese. The ripe spjO- 
rangium, moreover, is strongly oblique like that of Schizcea. 

As the sporocarp ripens the outer cells become excessively 
hard, especially the first layer of hypodermal cells (Fig. 256), 
whose walls become so thick as to almost obliterate the cell 
cavity. The second hypodermal layer is also thickened, but 
not so strongly. At maturity the sporocarp of P. Americana 
forms a globular body about 3 mm. in diameter, covered with 
hairs,, and attached to a long peduncle which bends downward 



.XI LEPTOSPORANGJATJE HETEROSPOREJE 439 

and buries the ripe sporocarp more or less completely in the 
earth. The statement^ that this species has but three cham- 
bers is incorrect, and except for the longer pedicel of the fruit, 
and a slightly thinner epispore in the upper part of the macro- 
spore, it corresponds exactly to P. glohiilifcra. The sporo- 
carp splits into four parts, corresponding to the four lobes of 
the young fruit, and the membranaceous margins of the leaf 
form a tough indusium surrounding the sporangia. This in- 
dusium is not, at least in P. glohulifera, readily pervious to 
water, and germination does not begin for a long time after the 
valves separate, unless the indusium is artificially opened. 
Except for the number and position of the sori, and the relative 
position of the two sorts of sporangia, Marsilia agrees exactly 
with Pilularia. The sorus canals form two longitudinal rows 
along the sides of the elongated fruit rudiment, which may be 
compared to a pinnate leaf. In Marsilia, occupying the middle 
line of each sorus, is a row of large tetrahedral cells, which 
form three sets of segments, like any three-sided apical cell. 
Each of these cells produces a group of sporangia. The ter- 
minal one, derived directly from the apical cell, is a macro- 
sporangium ; the smaller lateral ones, derived from its earlier 
segments, the microsporangia. 

Fossil Leptosporangiatce 

Sporangia of undoubted Leptosporangiatae are exceedingly 
rare in the earlier geological formations. Solms-Laubach (2) 
cites Hymenophyllites as probably being a genuine leptospo- 
rangiate Fern, and Zeiller (i) describes some isolated spo- 
rangia that seem to be much like those of the modern Gleich- 
eniaceae. Forms like the Osmundacese have also been de- 
scribed by various waiters, but no traces of Cyatheace?e or 
Polypodiacese have been yet detected in Palaeozoic formations. 
In the Jurassic, undoubted evidences of GleicheniacCcne, Os- 
mundacese, and Schizaeacese are found (Raciborski (i)), but 
the Polypodiaceae do not seem to have appeared until still later. 
The existence of the Hydropterides below the Tertiary is 
doubtful, but in the latter formation occur undoubted remains 
of the living genera Salvinia, Pilularia, and Marsilia. 

^Goebel (10), p. 240; Underwood (4), 2nd ed., p. 127; "Botany of Cali- 
fornia," vol. ii. p. 352. 



440 MOSSES AND FERNS chap. 

Affinities of the Leptosporangiat^ 

The Osmundaceae undoubtedly are intermediate between 
the Eusporangiatse and Leptosporangiatse, but with which 
order of the former their affinities are closest is difficult to say. 
Among the Ophioglossacese, the larger species of Botrychium 
and Helminthostachys show apparent close structural similar- 
ity to the Leptosporangiatse ; but, on the other hand, in the 
distinctly circinate leaves and the character of the sporangia, 
as well as the histology, the Marattiacese are certainly quite as 
nearly related. Apparently all of these forms are generalised 
types, springing from a common stock, but no two of them 
directly related. 

Among the Leptosporangiatse themselves the relationships 
are evidently much closer. A common type of prothallium 
and sporangium prevails throughout, even in the heterospo- 
rous forms. The four families, Osmundacese, Gleicheniacese, 
Cyatheacese, and Polypodiacese, form a pretty continuous 
series, of which the Polypodiacese are with very little question 
the latest and most specialised forms. This is evinced both by 
the geological record, which, so far as yet examined, shows 
that they were the latest to appear, and by the fact that at 
present they greatly outnumber the other Ferns, probably in- 
cluding at least 90 per cent, of all living species. The single 
genus Poly podium has over 400 species, probably as many as 
all the lower Ferns combined. These facts, together with the 
specialised character of all the parts, indicate that they are 
Ferns which have adapted themselves to modern conditions. 

The Schizseacese and Hymenophyllacese do not seem to 
belong to this main line, but are somewhat peculiar types, ap- 
parently belonging near the bottom of the series. The Hymen- 
ophyllacese, on the whole, approach most nearly the Gleichen- 
iacese, with which they agree in many points, both in the sporo- 
phyte and gametophyte, but they also recall the Osmundaceae, 
and possibly may form a branch somewhere between the two, 
but nearer the former. The peculiarities of the gametophyte 
are probably in large measure the result of environment, and 
the filamentous prothallium of some species of Trichomanes 
and Schizcea is beyond question a secondary and not a primary 
condition, and the prothallium is typically like that of the other 
Leptosporangiatse. The nearest affinities of the Schizseace^e 



XI 



LEPTOSPORANGIATJE HETEROSPOREAL 



441 



seem to be with the Osmundacese, but in the structure and ar- 
rangement of their vascular bundles they are more like the 
Gleicheniacese. 

Of the two families of the Hydropterides, the Salviniaceae 
shows several points of resemblance to the Hymenophyllacea:. 
The development of the leaves is strikingly like those of Hy- 
menophyllacese wnth reniform or palmate leaves, and the struc- 
ture of the sori almost identical. The absence of secondary 



Sslvim'a 




Azoltq 



^spdrangiata 



roots in Salvinia is suggestive also of the similar absence in 
some species of Trichomanes. The two-sided apical cell of 
the stem is, however, different from that of the few Hymeno- 
phyllacese examined, which all possess the pyramidal initial, 
but possibly further examination may show forms with an 
initial cell similar to that of AzoUa or Salvinia. 

The Marsiliacese, except for their marked heterospory, are 
typical leptosporangiate forms. The writer has been inclined 
to assign them a position near the Polypodiaceae, but recent 



442 MOSSES AND FERNS chap. 

work on these forms has led to a somewhat different conclu- 
sion (Campbell (26) ). Both the anatomical structure, and the 
character of the sporocarp and sporangium point to a not very 
remote affinity with the Schizseacese. This view would har- 
monise better with Belajeff's A^ews as to the structure of the 
antheridium in Marsilia. The two genera of the Marsiliacese 
are evidently very closely related, and of these Pihilaria ap- 
proaches nearer the homosporous Ferns. The accompanying 
diagram shows the relationship assumed here. 



CHAPTER XII 

EQUISETINE^ 

All of the living representatives of the second class of the 
Pteridophytes may without hesitation be referred to the single 
genus Eqiiisetiun, with about twenty-five species, some of which, 
e. g., E. arvense, are almost cosmopolitan. In the largest 
species, E. giganteiim, the stems reach a height of lo metres or 
more, but are slender, not more than 2 to 3 cm. in diameter, and 
supported by the surrounding trees and bushes. The smallest 
species is E. scirpoides (Fig. 281, B), whose slender stems are 
seldom more than 15 to 20 cm. in length, and often one milli- 
metre or less in diameter. In spite of these differences in size, 
the structure is remarkably uniform, both in gametophyte and 
sporophyte. The following account is based mainly upon a 
study of E. telmateia,^ but applies to the other species that have 
been studied. 

The Gametophyte 

The ripe spore of Eqiiiscttim is globular and shows no 
trace of the ventral ridges usually evident in tetrahedral spores. 
Four distinct membranes surround it, the inner one (intine) 
being exceedingly delicate, but with care showing the cellulose 
reaction (Buchtien ( i ) ) . Outside of this are the exospore and 
the elaters, between which lies another layer, "Mittelhaut" of 
Strasburger ((11), p. 199), belonging to the exospore. The 
well-known elaters (Fig. 257, A) form two strips attached in 
the middle and terminating in spoon-shaped appendages. The 
elaters are usually more or less spirally twisted, and when dry 
show faint oblique striations, except on the expanded ends. 
They are extremely hygroscopic, and respond instantly to any 

^ E. maximum Lam. 

443 



444 



MOSSES AND FERNS 



CHAP. 



changes in the moisture of the atmosphere. A careful study of 
the dehiscence of the sporangium shows that as it dries the 
expansion of the elaters assists very materially in opening it, 
and their function is something more than that of keeping the 
spores together, as has been asserted (Buchtien (i), p. 15). 
The striation of the elaters is merely the result of wrinkling by 
drying, and when moistened this disappears completely. The 
elaters show the cellulose reaction except upon the upper surface, 
which is cuticularised. 

The spores contain much chlorophyll, which in the dry 
spores appears amorphous and gives them a dark olive-green 
colour. So soon as the spore is moistened, however, it increases 



r„. 






Fig. 257. — In this and all the following figures of Equisetum, the drawings were made 
from E. telmateia (£. maximum. Lam.), unless otherwise indicated. A, ripe, dry 
spore with expanded elaters, Xi8o; B, a similar spore placed in water, Xi8o; C, 
D, germinating spores, X360; E, older stages of germination, X180; r, primary 
rhizoid. 



in diameter by about one-half through the absorption of water, 
and the numerous small round chloroplasts then become very 
evident. The nucleus is large, and occupies the centre of the 
spore. After a short time the elaters and the outer layer of 
the exposore are thrown off, and probably the rest of the ex- 
ospore, as no trace of this can be seen in the young prothallium. 
The spores quickly lose their power of germination, and 
should be sown as soon as they are discharged. If this is done 
germination begins almost at once, and within ten to twelve 
hours the first division wall may be completed. The chloro- 
plasts rapidly multiply by division and often show a distinct 
radiate arrangement, extending in lines from the nucelus to the 
periphery. The first division may occur before the spore has 



XII 



EQUISETINE^ 



445 



changed form, and in this case (Fig. 257, C) a small cell is cut 
off by a strongly curved wall. Both cells contain chlorophyll, 
but the nucleus of the smaller cell is smaller than the other. 
In other spores there is first an elongation, as in Osmiinda, and 
the smaller end, which like that has some chlorophyll, but not 
so much relatively as the larger, is cut off, and forms the first 
rhizoid, and within twenty-four hours, under suitable condi- 
tions, this may reach a length considerably exceeding the diame- 
ter of the spore. Sadebeck ( (6), p. 177) showed and Buchtien 





?XG. 258.— *Youngr profliariia of Equisetum, showing the variation in form, Xi8o. In A 
there is apparently a definite initial cell; r, rhizoid. 



((i), p. 29) confirmed this, that the first rhizoid is positively 
heliotropic. 

The first divisions in the prothallial cell are extremely vari- 
ous, in this recalling the behaviour of the eusporangiate Fili- 
cineae and the Osmundaceae. The first wall may be either ver» 
tical or transverse (Fig. 257), and sometimes, but not often, 
there are several transverse walls, and a short filament is 
formed. More commonly the first transverse wall is followed 
by a vertical wall in one or both cells. In case the first wall is 
vertical it not infrequently happens that the two cells, by re- 
peated transverse divisions, form two parallel rows of cells, 
which may diverge, so that the young prothallium becomes two- 
iobed. In a number of cases a two-sided apical cell was seen 
(Fig. 258), but its growth is very limited. Finally, a cell-mass 



446 



MOSSES AND FERNS 



CHAP. 



occasionally is the first product of germination. As a not 
infrequent occurrence may be mentioned also the suppression of 
the first rhizoid (Fig. 258, C). The development for some 
time is so varied that it is impossible to give any rule for it, but 
generally the prothallium at this stage, like that of the lepto- 
sporangiate Ferns, consists of but one layer of cells, and does 
not show a midrib. These prothallia also do not have a definite 
apical growth, and are usually more or less branched. Often, 





Fig. .TS9. — A, Female prothallium with the nrst archegonium (ar), X70; B, male pro- 
thallium, X70. 



however, the prothallium while still small has a somewhat cy- 
lindrical body composed of several layers of cells, and in these 
the rhizoids are mainly confined to the base. The chloroplasts 
which these at first contain are gradually changed into leuco- 
plasts, and may be completely absorbed (Buchtien (i), p. 17). 
A comparison of the gametophyte with that of Lycopodium 
cernuum has been made (Jeffrey (2), p. 186), but as Goebel has 
pointed out ((22), p. 409) there is this radical difference, — in 
Equisehim the prothallium is dorsi-ventral, as it is in the Ferns, 
while in Lycopodium it is radially constructed. The more or 
less evidently upright form assumed by the prothallium in 
Equisetum is due to the amount of light. Normally the pro- 
thallium of E. telmateia is not upright, but more or less decid- 
edly prostrate, as it is in the Ferns. (See Fig. 259, A.) 



XII 



EQUISETINE^ 



447 



The Sexual Organs 

The prothallia of Equisettim are usually dioecious and, as is 
usual in such cases, the males are smaller and the antheridia 
develop first. The latter generally appear in ahout a month. 
In E. telniateia there is not so much difference in the appear- 
ance and size of the male and female plants, and they are not 
always distinguishable by the naked eye. 

The first antheridia in E. pratense (Buchtien (i), p. 21), 
may appear within four weeks on vigorous prothallia, and are 
found at the tip, or upon the forward margin of the prothallium. 
After the first marginal antheridia are formed, there is inau- 
gurated an active division in the cells immediately adjacent, and 
a sort of meristem is developed from which new antheridia 





Fig. 260. — Development of the antheridium, X190. A, Longitudinal section through 
the antheridial meristem showing antheridia of different ages; B, longitudinal sec- 
tion of young antheridium, X375; C, two sections of a terminal, single antheridium, 
nearly ripe, X190; D, three transverse sections of young antheridium, X190; 
o, opercular cell. 



arise, much as is the case in E. telniateia. AMiile in the latter 
species, as in others, the antheridia may arise at the ends of 
the prothallial branches, they also may be formed upon a meris- 
tem cjuite like the archegonia, and are usually in groups, so that 
longitudinal sections show antheridia of very different ages, all 
evidently derived from the activity of the meristem (Fig. 260, 
A). The development shows a close resemblance to that of 
the eusporangiate Ferns, and in connection with the other points 
in the growth of the gametophyte and sexual organs, suggests 



448 



MOSSES AND FERNS 



CHAP. 



a nearer connection of these two groups than is usually admitted. 
As in the eusporangiate Ferns, the antheridium mother cell is 
divided into an inner and an outer cell of which the inner one 
forms at once the sperm cells. When the antheridium arises at 
the end of a filament, the divisions in the terminal cell are very 
much like those in Osmund a. In the mother cell three intersect- 
ing walls enclose a tetrahedral cell, which then has the cover cell 
cut off by a periclinal wall. In both forms of antheridium the 
subsequent history is the same. The central cell divides first 
by a transverse wall, followed by vertical walls in each cell, and 
subsequently by numerous divisions which show no definite 
arrangement (Fig. 260, C), and produce a very large number 
of sperm cells. In the cover cell only radial walls are formed, 




Fig. 261. — Development of the spermatozoids, Xiooo. A, Three of the central cells of 
an antheridium before the final division; B-D, final nuclear divisions in the sperm 
cells; E-J, development of the spermatozoid from the nucleus of the sperm cell; 
K, two free spermatozoids; v, the vesicle; b, blepharoplast. (I. J., after Belajeff). 



and it thus remains single-layered, as in Marattia and Osmunda. 
There is often a triangular cell (Fig. 260, D, 0), recalling the 
opercular cell in these forms. 

From the prothallial tissue adjacent to the sperm-cells, there 
is usually cut off a mantle of tabular cells enclosing the sperm- 
cells, much as is the case in Marattia and Botrychium. The 
dehiscence of the antheridium is caused by the separation of the 
cells of the outer-wall, but no cells are thrown off. 



Xn EQUISETINEAl 449 

Development of the Spermatozoids 

The large size of the spermatozoids of Eqitisctum makes 
them especially suitable for the study of their development, and 
this was traced with some care in E. telmateia. Belajeff (6), 
more recently, has studied the development of the si)ermatozoid 
in E. arvense. 

The nuclei of the sperm cells previous to their final division 
are globular and show one, sometimes two, small but distinct 
nucleoli, and numerous chromosomes. In exceptional cases the 
two blepharoplasts could also be seen. Previous to the final 
division the latter take their place on opposite sides of the now 
somewhat flattened nucleus, whose nucleolus cannot be distin- 
guished and whose chromosomes are very distinct, short, curved 
bodies. Their number could not with certainty be determined. 
The nucleus passes through the various karyokinetic phases, 
and the blepharoplasts occupy the poles of the nuclear spindle. 
The resting nuclei, as in other cases, show no nucleolus. Fig. 
261, F, shows the earliest stage in the differentiation of the 
spermatozoid, and this corresponds exactly with what I have 
observed in various Ferns, and differs somewhat from Buch- 
tien's figures of corresponding stages. The nucleus, which is 
not noticeably lateral in position, shows a narrow cleft upon one 
side. Seen in profile (Fig. 261, F, i), one side projects some- 
what more than the other, and becomes the anterior end, which 
later becomes thinner than the posterior part. I was unable to 
see that this forward part behaved differently from the hinder 
part with regard to the nuclear stain employed, nor could I sat- 
isfy myself of the presence of the cytoplasmic anterior prom- 
,inence which Strasburger ((n), IV., PI. m) figures in the 
Ferns. 

In some cases the blepharoplast could be seen (Fig. 261, E- 
H) and in the older stages this was much elongated, extending 
beyond the pointed end of the nucleus ; but perhaps owing to 
the fixing agent used — chromic acid — the formation of the cilia 
from the blepharoplast did not show at all clearly, while Belajeff 
indicates (Fig. 261, I) that they are very conspicuous. Per- 
haps also due to unsatisfactory staining, my preparations did 
not show at all clearly the cytoplasmic envelope about the nu- 
cleus which is so conspicuous in Belajeff's figures. (See Fig. 
261, J.) 

The body rapidly elongates and becomes quite homogeneous, 
29 



450 MOSSES AND FERNS chap. 

but this does not occur until a comparatively late stage. The 
nucleus is here somewhat flattened to begin with, and the coils 
of the spermatozoid lie nearly in the same plane and resemble 
a good deal those of Marattia, except that they are larger. The- 
protoplasm enclosed within the coils is conspicuously granular, 
and forms the large vesicle attached to the posterior coils of the 
free spermatozoid. The mucilaginous change in the walls of 
the sperm cells begins about the same time as the differentiation 
of the spermatozoids. 

The free spermatozoids consist of from two to three com- 
plete coils, of which the forward one or two are very much 
smaller than the very large and broad hinder one, which encloses 
the vesicle. The cilia are much like those of the Fern sperma- 
tozoid, but somewhat shorter. The cover cells of the ripe an- 
theridium are forced apart by the swelling of the mucilage from 
the disorganised walls of the sperm cells, which are forced out 
of the opening into the water, where the remaining wall of the 
sperm cell is dissolved and the spermatozoid set free. When 
in motion a peculiar undulation of the large posterior coil is 
conspicuous, a phenomenon which has also been observed in the 
quite similar spermatozoids of Osmunda. 

The young female prothallium is always a cylindrical mass 
of cells with a series of thin lateral lobes. After the archegonia 
begin to form and a definite apical meristem is established, the 
formation of these lobes is almost exactly like the similar ones 
in young plants of Anthoceros fusiformis. The exact relation 
of the growing point in the older prothallium to the primary 
one could not be made out. In the former this arises, according 
to Buchtien ( i ) , upon the under side of the prothallium, with- 
out any apparent relation to the primary growing point. This 
much is certain, that just before the first archegonium appears, 
there is formed a cushion not unlike that of the Ferns. In the 
youngest condition this in profile (Fig. 262, A) shows an evi- 
dent apical cell (probably one of several), not unlike that of the 
Ferns; but the great difficulty of obtaining accurate sections 
through it made it impossible to follow exactly its further de- 
velopment. This much can be stated confidently, however, 
that at the time when the first archegonia are produced, the 
structure of the prothallium is essentially that of Osmunda 
or Marattia, and consists of a central massive midrib and a 
one-celled lamina, which is not continuous, but composed of 



XII 



EQUISETINE^ 



451 



separate lobes. A similar condition exists in Osmuncia, where 
in the older prothallia similar but much shorter and broader 
lobes arise alternately from either side of the growing apex. 

The development of the archegonium is intimately associated 
with the formation of the lobes. The archegonium mother cell 
is formed close to the base of the young lobe upon the ventral 
side. By subsequent growth of the tissue between it and the 
apical meristem, it is subsequently forced to tlie upper side, but 
its origin is ventral, as in the Ferns. The lobe at whose base 




Fig. 262. — Development of the archegonium. A, Optical section of the very young 
archegonial meristem, X225; B-E, longitudinal sections of young archegonia, X450; 
Cj neck canal cell; v, ventral canal cell; o, egg. 



it is borne grows for some time by a definite apical cell, which is 
very evident in horizontal sections (Fig. 263, C). 

The development of the archegonium most nearly resembles 
that of the eusporangiate Ferns. Usually, but not always, no 
basal cell is formed, and the first division in the inner cell sepa- 
rates the neck canal cell from the central cell. Both neck and 
ventral canal cells (Fig. 262, E) equal in breadth the central 
cell, and in this respect are most like the Marattiaceae. The 
neck canal cell later grows up between the neck cells, but there 
is usually a space between its summit and the terminal neck 



452 



MOSSES AND FERNS 



CHAP. 



cells, which here are much longer than the others. It subse- 
quently divides by a transverse wall, as may happen in the 
Marattiacese and occasionally in Osmunda, but whether this 
always takes place is not certain (Fig. 263, A). The four rows 
of neck cells are all alike, and consist ordinarily of three cells 




Fig. 263. — A, Longitudinal section of nearly ripe archegonium, with two neck canal 
cells (c, c^ Xsso; B, section of an open archegonium, X275; C, D, two cross- 
sections of a young archegonium; L, the lobe at the base of which the arche- 
gonium is formed, Xsso. 



each, the terminal ones being very long, and when the archego- 
nium opens bending back strongly, but not becoming detached. 
The central cell is surrounded by a single layer of tabular cells 
cut off from the adjacent prothallium tissue, but these divisions 
may extend to the lower neck cells (Fig. 263, A). The ^gg 
is globular and shows no peculiarities of structure. Buchtien's 
((i), p. 24) account of the further development of the mer- 
istem, as well as his figures, point to something very much like 
a repeated dichotomy of the growing point ; a further investiga- 



XII EQUISETINETE 453 

tion of the exact origin of the ])rimary meristem and its relation 
to the secondary ones found in tlie branches is much to be 
desired. 

Jeffrey finds in E. arvense, E. hicmale, and E. limosum, that 
the neck canal cell usually divides longtitudinally, and compares 
it with the divisions in the archegonium of Lycopodhim 
phlegmaria. This division may take place in E. telmatcia, but 
is exceptional. It may be mentioned that a similar division has 
been observed in Marattia Douglasii. 

Each archegonium stands between two lobes, the one from 
whose base it has itself developed, and the next younger one. 
As these lobes in vigorous prothallia grow to a large size, and 
branch, this gives the prothallium an extremely irregular out- 
line, recalling very much that of Anthoccros punctatiis or A. 
fiisiformis. These branching lobes are not to be confounded 
with the branches of the prothallium body due to the dichotomy 
of the archegonial meristem. These latter are always short, 
and project but little compared to the secondary branching lobes 
produced from them. The entrance of the spermatozoids and 
the changes subsequent to fertilisation seem to be exactly the 
same as in Ferns. 

The prothallia are normally dioecious, but this is not ex- 
clusively the case. To a certain extent the external conditions 
influence the production of males or females, as in the Ferns, 
and unfavourable conditions of nutrition tend to increase the 
proportion of the former. 

According to Hofmeister (i) the number of archegonia 
upon vigorous prothallia varies from twenty to thirty. His 
statement that this exceeds the number of antheridia in the 
larger male prothallia is not confirmed by Buchtien, who found 
as many as 120 of the latter in some cases. 

Usually more than one archegonium is fertilised, Hof- 
meister having found as many as seven embryos upon a single 
prothallium. He does not state how many of these develop. 
The embryo corresponds closely to that of the Ferns, and has 
been carefully described by Sadebeck (6). 

The Embryo 

The fertilised Q:gg growls until it completely fills the ventral 
cavity, and its granular contents become more separated, and 



454 



MOSSES AND FERNS 



CHAP. 



the nucleus is decidedly larger than before fertilisation. The 
lower neck cells approach and apparently become grown to- 
gether, and as the divisions in the lower neck cells here contrib- 
ute to the calyptra, the young embryo becomes more deeply 
sunken in the prothallial tissue than is common in the Ferns. 
The basal wall is transverse, as in the Marattiacese, and the 
formation of the quadrants takes place as usual. The position 
of the quadrant walls is, however, sometimes slightly different, 




Fig. 264. — A, Longitudinal section of the venter of a recently fertilised archeg'onium, 
X300; B, a similar section of an archegonium with the young embryo; C, D, two 
transverse sections of a somewhat older embryo, X300; st, apical cell of the stem; 
r, apical cell of the root; E, longitudinal section of an older embryo, X300; I, I, 
the basal wall. 



being often decidedly inclined in both epibasal and hypobasal 
halves (Fig. 264, E). In the former the larger of the two 
primary cells is the initial for the stem, and its large size, com- 
pared to the leaf quadrant, already points to the greater develop- 
ment of the stem in the sporophyte compared to the leaves. Of 
the hypobasal quadrants the larger becomes at once the root, 
whose axis is nearly coincident with that of the stem. 

Jeffrey ( (2), p. 169) thinks that in E. hiemale the root also 
may be of epibasal origin, but his figures 7 and 8 are capable of 



xn 



EQUISETINEJE 



455 



a different Interpretation, and to judge from them it is quite as 
likely that the root is hypobasal as in the other species examined. 
The first two divisions in the stem quadrant establish the defini- 
tive apical cell, which occupies nearly the centre of the epibasal 
part of the embryo, and is surrounded by a circle of four cells, 
two of which belong to the leaf quadrant (Fig. 225, C) , and two 
are segments of the stem quadrant, the first one corresponding 
morphologically to the second leaf of the Fern embryo. This 




Fig. 265. — A, An advanced embryo of E. arvense, surface view, X360; B, optical 
section of a similar stage of E. palustre, X360; older embryo of E. arvense, X160; 
St, stem; R, root (all the figures after Sadebeck). 



Circle of cells forms the first sheath about the stem of the young 
sporophyte. After one set of lateral segments has been cut off 
from the root quadrant, the primary cap cell is formed as in the 
Ferns. Unlike the latter, the divisions in the stem apex proceed 
rapidly, and it soon projects in the centre of the embryo as a 
broad conical prominence, terminating in the large tetrahedral 
apical cell. 

The three parts of which the primary leaf-sheath is com- 
posed remain distinct and form the three teeth (Fig. 265, C), 
which grow rapidly until they are about on a level with the 
apex of the stem. This growth Is mainly due to the activity 
of the marginal cells. The root grows less actively at first than 
either stem or leaves, and at the time the latter Is nearly fully 
developed forms but a small protuberance at the base of the 
embryo (Fig. 265, C). The foot at this time Is not consplcu- 



456 MOSSES AND FERNS chap. 

ous, but later enlarges more. Its cells are in close contact with 
the prothallial cells. The root now grows rapidly downward, 
penetrating through the prothallium until it reaches the ground. 
The stem apex rapidly elongates and grows upward through the 
calyptra. The embryo thus perforates the prothallium both 
above and below, as in Marattia, although owing to the position 
of the archegonium in the former, the relation of the embryo to 
the archegonium is not the same. 

The root in E. hiemale and E. arvense (Jeffrey (2), p. 169) 
penetrates the earth before the shoot breaks through the calyp- 
tra, but in E. limosum, the emergence of the root occurs at a 
much later period. At the time the shoot emerges from the 
calyptra, there is already developed the rudiment of the bud 
that is to form the second shoot. This bud is formed above the 
origin of the primary root, between two of the primary leaf- 
traces. At this time there are already developed three or more 
leaf-whorls about the shoot-axis. The second shoot does not 
develop its first root until its first foliar sheath is well developed. 

In most species that have been studied, the primary shoot 
has the leaves of the whorls in threes, but in E. variegatum 
(Buchtien (i), p. no) there are regularly but two leaves in 
each whorl, and Jeffrey found that this was sometimes the case 
in E. limosum. 

The development of the primary axis, unlike that of the 
Filicinese, is limited, and it ceases growing after producing ten 
to fifteen sheaths, which, like the first one, are three-toothed. 
The stem remains very slender, but shows the marked division 
into nodes and internodes found in the later ones. This pri- 
mary stem has irregular lacunae in the cortex, but does not show 
the cavity so conspicuous in the central part of the older plant, 
and in E. telmateia, according to Buchtien, this is quite solid. 
In this species he figures four vascular bundles, whose xylem is 
relatively much better developed than in the later stems. The 
bundles, like all of those in the stem and leaves, are collateral, 
and the whole group is surrounded by a well-marked endo- 
dermis. From the base of this primary shoot a second stronger 
one develops. This second shoot is much more vigorous, and 
its leaf-sheaths have four teeth. From the base of this others 
arise in the same way and in rapid succession. Sometimes the 
third, or one or more of the later formed basal shoots, bends 
downward and penetrates the earth, producing the first of the 



XII EQ VISE T4NEJE 457 

characteristic rhizomes. The first of these have also four- 
toothed sheaths, but the branches procUiced from them gradually 
assume the characters of the fully-developed shoots, some of 
which ultimately bear sporangia. The first shoots of the sporo- 
phyte, even in such species as later branch very freely, produce 
only an occasional branch, which breaks through the base of the 
sheath. 

In E. hiemalc, there is found, according to Jeffrey, a gradual 
transition from the typical arrangement of the tissues of the 
root, to those in the base of the young shoot. There is first 
developed in the latter an unbroken tube of reticulate tracheids, 
which Jeffrey considers to be a reversion to an originally cylin- 
drical stele. However, as this same arrangement is repeated 
in the succeeding nodes, it seems much more likely tliat this 
ring of tracheary tissue merely represents the basal node. 
Within the ring of tracheary tissue is a mass of parenchyma, 
and outside a zone of phloem bounded by a typical endodermis. 
The rudiment of the second shoot causes a break in the vascular 
ring above its point of origin. In the internode there are three 
vascular strands, corresponding to the three teeth of the foliar- 
w^horl. In short, the structure of the primary shoot is essen- 
tially the same as that of the stouter shoots developed subse- 
quently. Although Jeffrey speaks of a "central-cylinder," there 
is nothing in his account to show that the vascular bundles do 
not originate from the primary cortical tissue, as they do in the 
adult shoots. 

The Mature Sporophyte 

On comparing the sporophyte of Eqiiisetum with that of 
most Ferns, the greatest contrast is in the relative importance 
of stem and leaves. The stem in all the Equisetinese is extra- 
ordinarily developed, while the leaves are rudimentary, in strong 
contrast to their great size and complexity in most Ferns. All 
species of Eqiiisetum produce a more or less developed under- 
ground rhizome, which often grows to a great length and rami- 
fies extensively. This, like the aerial branches developed from 
it, shows a regular series of nodes and internodes. The latter 
are marked by longitudinal furrows, and about each node is a 
sheath whose summit is continued into a number of teeth, vary- 
ing with the size of the stem. Corresponding to each tootK 



A. 




Fig. 266. — A, Upper part of a fertile shoot of E. telemateia, X i ; B, lower part of a 
vegetative shoot, with young branches for the next season's growth, X i ; T, tubers; 
C, cross-section of an internode of the fertile shoot, X4; L, cortical lacunae; D, 
sporangiophores,- X4; E, median section of a single sporangiophore, X6; sp, 
sporangia. 



XII EQUISETINE^ 459 

of the sheath there is developed an axillary bud, which may 
either at once develop into a shoot, subterranean or aerial, or 
these buds may remain dormant for an indefinite period, being 
capable of growing, however, under favourable conditions. 
The surface of the rhizome in E. telmatcia, especially at the 
nodes, is covered with a dense dark-brown felt of matted hairs, 
and a whorl of roots occurs at each node, corresponding in num- 
ber to the number of axillary buds, from whose bases the roots 
really grow. Sometimes the buds become changed into tubers 
(Fig. 266), which are especially common in E. telmatcia and E. 
arvense. These tubes are protected by a hard brown scleren- 
chymatous rind, within which is a mass of starchy parenchyma, 
traversed by the slender vascular bundles. In some cases these 
buds form in chains and are then seen to be the swollen inter- 
jiodes of short branches. 

The aerial stems are of two kinds, sporiferous and sterile. 
In one group the only difference between the two is that the 
former bear at the apex the sporangial strobilus ; in the second, 
of which E. telmafeia is an example, the sporiferous branches 
are almost entirely destitute of chlorophyll and quite un- 
branched, while the green sterile shoots are extensively 
branched. In such forms the fertile shoots die as soon as the 
spores are shed, and usually appear before the green shoots are 
developed. 

The Stem (Rees (2) ; Sachs ( i) ; Janczewski ( j) ; Jeifrey {2)) 

A longitudinal section of one of the numerous subterranean 
buds (Fig. 267) shows that the conical apex of the stem is 
occupied by a large pyramidal cell whose segmentation is ex- 
ceedingly regular. The youngest of the foliar sheaths is sepa- 
rated from the apex by several segments, but below, the next 
older sheath is very close to it, and the internode, which in the 
older stem is so conspicuous, is scarcely perceptible. The 
closely-set sheaths grow very rapidly, so that all but the young- 
est ones extend beyond the stem apex, which is thus very com- 
pletely protected. They form a compact, many-layered cover- 
ing about it, presenting very much the appearance of the leaf- 
buds of many Spermaphytes. The apical cell shows the usual 
three series of lateral segments. These are arranged in three 
rows, but owing to a slight displacement in the younger ones, 



460 



MOSSES AND FERNS 



CHAP. 



the teeth of the sheaths alternate. Each cycle of three seg- 
ments comes to lie practically in the same plane, and consti- 
tutes a disc which later forms a node and internode of the stem. 
Each segment is first divided by a wall nearly parallel to the wall 
by which it was cut off from the apical cell, into two overlying 
cells. The upper cells or semi-segments give rise to the nodes, 
the lower to the internodes. 

The next walls are like the sextant walls in the roots of 
the Ferns, and a cross-section just below the apex presents 
exactly the same appearance. Each cell now divides by walls, 




Fig. 267. — A, Median section of a strong subterranean (vegetative) bud, X30; k, 
lateral bud; B, the apex of the same section, X200. 



•apparently not always in the same order, parallel with the 
primary and lateral walls, and very soon there are periclinal 
divisions by which an inner cell is cut off from each segment 
cell that extends to the centre. This primary group of central 
cells is the pith, which later in the internodes is usually torn 
apart and destroyed, leaving the large central hollow met with 
in all the larger species of Eqiiisetum. From the outer cells 
are developed the leaves, the vascular bundles, and cortex. 

The annular leaf-sheaths begin as outgrowths of the super- 
ficial nodal cells of each cycle of segments, and these form a 
circular ridge or cushion running round the base of the apical 
cone. The summit of this ridge is occupied by a row of mar- 
ginal cells, which are the initial cells, and from these segments 
are cut off alternately upon the inner and outer sides (Fig. 272, 



XII 



EQUISETINE^ 



461 



A). The growth is stronger at certain points, which, according 
to Rees, have a definite relation to the early divisions. Thus in 
E. scirpoidcs the teeth are always three, and correspond to the 



A. 





Fig. 268. — Transverse section of a young vegetative shoot just below the apex, X260; B, 
outer part of a section lower down, X260; pr, procambial zone; C, young vascular 
bundle, X520; t, primary tracheids. 



primary nodal cells; in E. arvense there are six or seven, in 
the first case corresponding to the sextant cells, in the latter to 
the sextant cells plus the first division in one of them. In the 



462 MOSSES AND FERNS chap. 

large species, like E. telmateia, it is difficult to trace any such 
relation. In most forms, by subsequent dichotomy of some or 
all of the primary teeth, others are formed, so that the number 
in the fully-developed sheath exceeds that hrst formed. As 
soon as the young sheath begins to project, a section through 
one of the teeth shows that it is divided into an upper and lower 
tier of cells, the apical cell terminating the upper one. This 
division no doubt corresponds to the first horizontal division in 
the outer nodal cell from which the leaf-tooth originally comes. 
In one a little older (Fig. 272, B), in this upper tier of cells a 
line of cells occupying the axis is evident {fh), extending from 
the base of the leaf nearly to the summit, and growing at its 
outer end by the addition of cells derived from the inner part of 
the youngest upper segments of the terminal cell of the leaf.^ 
This is the beginning of the single vascular bundle found in each 
leaf. 

Shortly after this first indication of the vascular bundle of 
the leaf can be seen, the cells of the cortex immediately outside 
the central pith begin to divide rapidly by longitudinal walls and 
form a zone of cambiform cells completely surrounding the 
medulla. In the primary central row of cells in the leaves 
similar divisions occur, and. a very evident procambium cylinder 
is formed, bending in and joining the procambium zone of the 
cortex. At the point of junction the cells are shorter and 
broader, and the cortical cells lying outside are also much 
broader, so that the cortical procambium is very conspicuous. 
If cross-sections are examined about this time, in the procam- 
bium zone are found a number of groups of cells where the 
divisions are more rapid, and the resulting cells narrower than 
the surrounding ones. These are the separate vascular bundles, 
and are continuous with those in the leaves (Fig. 269). The 
first permanent tissue consists of one or two small annular 
tracheids upon the inner side of the bundle (Fig. 268, C). 
These are followed by several others. They first form in the 
internodal part of the bundle and only later in the foliar portion. 
The nodal tracheids joining the xylem of the foliar and inter- 
nodal bundles are very irregular short cells with annular thick- 
enings upon their walls. Later two small groups of larger 
spiral tracheae are formed at the side's of the xylem, but the 

' Each tooth is here regarded as a leaf, the sheath as a circle of con- 
fluent leaves. 



XII 



EQUISETINEJE 



463 



greater part remains but little changed. By this time, in 
E. telmatcia, numbers of cells with peculiar contents are noticed 
scattered through the pith and cortex (Fig. 269). The con- 
tents of these are dense, and stain deeply, indicating the presence 
of mucilaginous matter, and probably tannin, their appearance 
and behaviour being very much like the tannin cells of Angiop- 
teris or Marattia. 

In the older parts of the section the nodal cells remain short, 
while the internodal cells elongate very much and separate the 
nodes with their attached foliar sheaths. With this growth is 
associated the formation of the characteristic lacunae. In all 




Fig. 269. — Longitudinal section of the young stem, showing the junction of the foliar 
and internodal bundles; tr, the primary tracheids; x, x, tannin-bearing cells. 

the large species the growth of the medullary cells very soon 
ceases to keep up with the expansion of the stem, and they are 
torn apart and almost completely disappear, leaving a great cen- 
tral cavity in each internode separated from the neighbouring 
ones by a thin diaphragm, — all that is left of the medulla in the 
fully-developed stem. The leaves of successive sheaths alter- 
nate, and a study of the course of the vascular bundles shows 
that at each node the alternating bundles of successive inter- 
nodes are connected by short branches. Corresponding to the 



464 MOSSES AND FERNS ckap. 

vascular bundles are ridges upon the surface of the internodes 
and foliar sheaths, due to greater growth at these points, 
as a result of which a regular series of cortical lacunae (vallecu- 
lar canals) is formed, alternating with them (Fig. 266, C), 
and lying just outside of the cortical zone containing the vascu- 
lar bundles. In some of the small species of Equisetum, as in 
the primary shoot, the central lacuna is absent. 

A cross-section of the fully-developed stem of E. telmateia 
(Fig. 266, C) shows this very regular arrangement of the vas- 
cular bundles and lacunse. In addition to the large cortical 
ones, each vascular bundle has, on the inner side, a large air- 
space, which like the other is formed by the tearing apart of the 
tissues of the bundle. In this way the primary tracheids are 
torn apart and often destroyed, so that all that remains of them 
are the isolated thickened rings adhering to the sides of the 
canal. The bundle is strictly collateral in structure, and very 
much resembles that of many grasses and other simple Mon- 
ocotyledons. The phloem is composed of sieve-tubes, which, 
according to Russow (i), have only horizontal sieve-plates, 
and no lateral ones as in the Ferns. These are mingled with 
cambiform cells. In the species in question there is in addition 
a zone of bast fibres at the outer limit of the phloem. 

Surrounding the whole circle of bundles in E. telmateia, 
E. arv^ise, and several other species, there is a common endo- 
dermis (Fig. 270, en). In others the arrangement is different 
(Pfitzer (i) ; Van Tieghem (6)). Thus in E. limosum, each 
separate bundle has its own endodermis ; in E. hiemale there is 
a common inner as well as an outer endodermis in the aerial 
stems, while the bundles of the rhizome are like those of E. limo- 
sum. Inside the endodermis lies the single pericycle. 

There has been some controversy as to the nature of the vas- 
cular system in Equisetum. Van Tieghem (6, 8) describes the 
stem of Equisetum as ''astelic"; Strasburger ((11), vol. 3) 
considers it as monostelic. Jeffrey has attempted to reduce the 
structures to his "siphonostelic" type, i. e., he would compare 
the complex of vascular bundles to the cylindrical stele of the 
Ferns and Lycopods. The spaces between the vascular strands 
of the internodes he considers as "gaps" comparable to the foliar 
gaps in the stele of the Ferns, or the ramular gaps in the stele 
of the Lycopods. He is, moreover, of the opinion that the solid 
stele C'protostele") found in the fossil Sphenophyllales is the 






XII 



EQUISETINEJE 



465 



prototype of the "siphonostele," which he thinks is the condition 
found in Equisetum. He seems, however, to have overlooked 
the fact that in the adult shoot, at least, of Equisetum, the whole 
vascular system of the stem originates from the primary cortex 
or periblem, the original central tissue-cylinder giving rise only 
to the pith. Moreover, his assumed "ramular gaps" are found 
equally developed whether branches are developed or not, and 
are obviously related to the leaf-traces of the internode. 

All the cortical cells are separated by small intercellular 
spaces, which are .very conspicuous in the soft tissue of the 




Fig. 270. — Transverse section of the vascular bundle of a fully-developed vegetative 
shoot, X75; i, i, lacunae; x, x, tannin cells; t, t, remains of the primary tracheids; 
en, endodermis. 



fertile stems of E. telmateia and E. arvense. In all of the inter- 
nodes of the main axes of E. telmateia chlorophyll is absent, 
but in most species the principal assimilative tissue is situated 
here. It consists usually of isolated masses of transversely ex- 
tended green cells separated by strands of colourless sclerenchy- 
matous fibres, which form the ridges so prominent upon the in- 
ternodes and foliar sheaths. Seen in cross-section the masses of 
30 







o 



.0 



0<* 

Of) 






^,9^ 



"■r^ 



'r-V>^^ 






'9 

> 






\ 



) 



J 




Fig. 271. — Development of the stomata. A-C, Surface views of very young stomata of 
E. telmateia, X600; D, section of an older stoma of E. limosum, X700 (after 
Strasburger) ; E, outer surface of a complete stoma of E. telmateia, showing the 
silicious nodules upon the epidermal cells; F, inner side of the same, showing the 
silicious bars upon the inner walls of the guard cells; v, v, accessory cells; s, 
guard cells. 



XII EQUISETINEJE 467 

green cells are concave outwardly and lie l)eneath the ridges. 
In secondary branches the amount of this tissue is much greater 
and the lacunae less conspicuous, or indeed even wanting. 

The epidermis, as is vvell known, contains great quantities of 
silica, which gives it its very rough and harsh surface. This 
is deposited either uniformly, as is usually the case in the lateral 
cell walls, or in tubercular masses. Upon the inner surface of 
the guard cells of the stomata it forms regular transverse bars 
(Fig. 271). Upon the outer walls of the epidermal cells the 
masses form either isolated bead-like projections or these are 
more or less completely confluent. 

The stomata are peculiar in structure, and their development 
v^as first correctly described by Strasburger (i). In E. tcl- 
mateia these only occur usually upon the foliar sheaths, but in 
species with green internodes they are found principally upon the 
sides of the furrows over the green hypodermal tissue.^ Before 
the stoma proper is formed, the cell divides twice by longitudinal 
walls (Fig. 271), and the original cell is thus divided into a 
central one (the real stoma mother cell) and two narrow lateral 
accessory cells. The central cell now divides again, and the 
division wall splits in the centre as usual. A cross-section of 
the young stoma (Fig. 271, D) shows that the walls by w'hich 
the accessory cells are cut off are inclined, so that the stoma 
cell is broader at the bottom than at the top, and as develop- 
ment proceeds the accessory cells completely overarch the stoma, 
and in the older ones look as if they had arisen by horizontal 
divisions in the primary guard cells. The accessory cells show 
the same tuberculate silicious nodules upon their outer walls as 
the other epidermal cells, and upon the inner face of the real 
guard cells only are formed the regular bars. Stomata are quite 
absent from the rhizome, and also from the colourless fertile 
branches of E. tchnatcia. Compared with the aerial stems, the 
rhizome shows a smaller number of vascular bundles, and a cor- 
responding reduction in the number of the lacunae. 

The Branches 

Until the researches of Janczewski (3) and Famintzin (i) 
it was supposed that the lateral branches arose endogenously. 

^ Miss E. A. Southworth (i) found that in E. arvense they occur upon 
the ridges, and upon the fertile as well as the sterile shoots. 



468 



MOSSES AND FERNS 



CHAP. 



Their researches, however, showed conclusively that this was 
not the case, but that the origin is exogenous. In most species 
they are produced abundantly, and a bud is formed in the axil 
of each leaf, although it frequently happens that some of them 
do -not develop fully. In E. telmateia they do not occur at all, 
as a rule, upon the colourless sporiferous shoots, but are regu- 
larly formed from all but the lowest nodes of the sterile stems. 





Fig. 272.— Longitudinal section of a young vegetative shoot showing two young 
leaves (L.), X200; B, section passing through the base of a, somewhat older leaf; 
fh, vascular bundle; C, section passing through a young bud (&). 



In E. scirpoides they are absent from all the aerial stems, but 
whether rudiments of them are formed does not seem to have 
been investigated. 

Their development may be readily traced in a series of 
median longitudinal sections through a vigorous sterile stem of 
E. telmateia or E. arvense before it appears above ground. The 
young bud (Fig. 272, C) originates from a single epidermal 
cell just above the insertion of the leaf. This cell enlarges and 
is easily recognisable. In it are formed three intersecting walls 
cutting out the apical cell, which at first is somewhat irregular, 
but soon assumes its definite form, and the subsequent growth 
of the branch resembles in all essential points that of the main 



XII 



EQUISETINEJE 



469 



shoot. Very early the cells of the leaf-base immediately above 
the young bud grow around it like a sheath, and finally become 
grown together with the epidermal cells of the axis above tlie 
bud, which thus lies in a completely closed cavity. As the bud 
grows it gradually destroys the tissue surrounding the cavity, 
and finally breaks through the base of the leaf, appearing from 
the outside as if it had developed from below and not from the 
axil of the leaf. In most species these branches remain simple, 




Fig. 273. — Section of a lateral bud, enclosed within the sheath formed by the leaf-base, 

X175. 



but in E. sylvaticum and E. giganteum the secondary branches 
also ramify. 

The Roots 

The formation of the roots is intimately connected with that 
of the lateral buds. Each bud normally produces a single root 
below the first foliar sheath, which in the buds derived from the 
rhizome all develop, whether the buds themselves grow further 



470 



MOSSES AND FERNS 



CHAP. 



or not. According to Janczewski, certain of these rhizogenic 
buds of the rhizome produce several roots, but the buds remain 
otherwise undeveloped. In the aerial stems the roots remain 
normally undeveloped, but may often be stimulated into growth 
by keeping the stem moist and dark. 

Van Tieghem ((5), p. 55.1) describes the roots of E. palus- 
tre as being exogenous, and says they can be traced to a definite 
cell of one of the young segments. Janczewski ((3), p. 89), 
however, was unable to recognise the young root until the first 





Fig. 274. — A, Longitudinal section of the root apex, X200; x, x, the large central ves- 
sel of the vascular bundle; B, C, two transverse sections passing through the apex, 
X200. In C is shown the first divisions of the cap cell. 



foliar sheath was well developed, and in E. telmateia I could see 
no trace of the root in still older buds, and they were apparently 
always of endogenous origin, although this point was not spe- 
cially investigated. 

The structure of the apical meristem is much like that of 
the leptosporangiate Ferns, the main difference being the greater 
development of the root-cap, in which periclinal walls are fre- 
quent, so that the older layers, especially in the middle, are 
several cells thick, and not clearly limited. 

After the sextant walls are formed, each semi-segment is 



XII EQUISETINEAL 471 

divided at once into an inner and an outer cell, the former 
giving rise directly to the plerome or central cylinder. The 
next division (seen in longitudinal section) separates the epi- 
dermis initials from the cortex. A cross-section of the young 
plerome immediately after the first divisions have taken place 
(Fig. 275, A) shows that the three primary cells are of unec|ual 
size, and that the two smaller ones divide first. From the larger 
one, the first periclinal wall separates a central cell, which occu- 
pies almost exactly the middle of the section, and this stands 
immediately above the corresponding one in the older segments, 
so that in longitudinal sections (Fig. 274) these form a very 
conspicuous axial row of cells {x, x), which together constitute 





Fig. 275. — Three transverse sections of the young root, X200; tn, endodermis; v, cen- 
tral vessel. 

the single large vessel which occupies the centre of the older 
bundle. The endodermis becomes separated by this time, and 
a little lower down divides by periclinal walls into the two layers 
found in the completely developed root. The tissues of the cen- 
tral part of the young root are very regularly disposed (Fig. 
275, B, C). In the centre is the large vessel already described, 
around which are arranged at first a single row of usually six 
or eight cells (Fig. 275, B). By these first divisions the sepa- 
ration of the xylem and phloem of the bundle is complete. If 
there are six of these primary cells the bundle will be triarch, if 
eight, tetrarch. In somewhat older sections of a tetrarch bun- 
dle (Fig. 275, C) four of the primary cells are still recognis- 
able and have divided but little. These form the four groups 



472 MOSSES AND FERNS chap. 

of tracheids of the older bundle. The Intermediate cells divide 
much more rapidly and constitute the phloem. The number 
of endodermal cells in a cross-section corresponds generally to 
the number of xylem and phloem masses. The peripheral 
groups of tracheae early develop spiral thickenings upon their 
walls, and sometimes there is but a single row of tracheae in each 
xylem mass. Each of the three phloem masses of E. variega- 
turn has three narrow sieve-tubes in contact with the inner endo- 
dermis surrounded by thin-walled cambiform cells. The thick- 
enings upon the walls of the large central vessel form only at a 
late period. 

Intercellular spaces arise at the angles of the outer endo- 
dermal cell, and similar ones also between the outer cells of the 
cortex, which becomes very spongy in the older roots. Numer- 
ous brown root-hairs, like those upon the rhizome, cover the 
surface of the root. A pericycle is quite absent, and the sec- 
ondary roots arise from the inner endodermis in direct contact 
with the tracheids. The latter, as will be seen from the figure, 
lie between two endodermal cells, and the young root lies there- 
fore not directly opposite, but to one side of the corresponding 
xylem mass. The young roots may arise from either of these 
endodermal cells, and consequently there is formed a double 
row of rootlets corresponding to each xylem mass of the 
bundle. Shortly after the rootlet is formed, the endodermal 
cell outside it divides by a tangential wall, and this develops into 
a double layer of cells completely enclosing the young rootlet 
(Van Tieghem (5), p. 395). A similar ''digestive pouch" is 
formed, according to Van Tieghem, in the roots of many Ferns, 
but is in these derived from the cortex outside the endodermis. 
The double endodermis of the bundle of the older root shows 
the characteristic foldings of the radial walls only upon the outer 
cells. 

Cormack ( i ) has recently published a paper showing that in 
E. maximum ( telmateia) there is a slight secondary increase in 
thickness in the nodes of the stem, due to the presence of a 
genuine cambium, not unlike that in the stem of Botrychium. 

The Sporangium (Bower (15)) 

In all species of Equisetum the sporangia are formed upon 
the under side of peltate sporophylls arranged in closely-set 



XII 



EQUISETINE^ 



473 



circles about the upper part of the axis of the fertile shoots 
(Figs. 266, 281). A section through the apex of the young 
shoot shows much the same structure as a sterile one, but the 
apical cell is smaller and the leaves do not arise so near the sum- 
mit. Circular foliar sheaths are formed in the same way, but 
the leaves form rounded elevations, either entirely separated or 
but slightly joined (Fig. 276). These are at first nearly hemi- 
spherical, but soon become constricted at the base, and about the 
same time the first trace of the sporangia can be seen. A sec- 
tion of the young sporophyll shows that the centre of the promi- 





FlG. 2y6. — A, Longitudinal section of the apex of a young fertile shoot, Xi6; B, apex 
of the same, Xi6o; sp, young sporangiophore; x, apical cell. 



nence already has formed the young plerome which, as in the 
ordinary leaves, joins that of the internode beneath. Just above 
the base a cell may sometimes be detected, which is larger than 
its fellows, and has a larger nucleus. From a comparison wnth 
slightly older stages there is no doubt that this is the sporan- 
gium mother cell, or more correctly the axial sporangial cell, as 
the adjacent tissue also takes part in its further growth. This 
axial cell now becomes separated into an inner and outer cell, 
as in Botrychium. The outer cell divides again. The inner- 



474 



MOSSES AND FERNS 



CHAP. 



most cell of the axial row is the archesporium, and gives rise to 
the sporogenous cells by repeated divisions, at first at right 
angles to each other, later in aU directions. Bower ((15), p. 
497) thinks that all the sporogenous cells are not to be traced 
back to the single archesporial cell, but that the inner of the 
two cover cells also takes part in spore-formation. The exact 
limits of the archesporium are difficult to follow, as the contents 
of the sporogenous cells are not strikingly different from the 




Fig. 277.— a, Longitudinal section of young sporangiophore, showing the primary 
sporangial cell isp), X260; B, C, longitudinal sections of young sporangia, X260. 
The archesporial cells are shaded. 



inner tapetal ones. These are derived from the cells adjacent 
to the axial row, and from the cells of the latter just outside the 
archesporium. The wall of the sporangium is mainly formed 
from the cells adjacent to the axial row of cells. All the cells 
grow and divide rapidly, so that the sporangium soon projects 
strongly from the margin of the sporophyll, whose upper part 
becomes broad and flattened, while the stalk increases but little 
in diameter. The wall of the sporangium at first is three or 
four cells thick, Finally it is reduced to but a single completer 



XII 



EQUISETINEJE 



A7S 



layer by the absorption of the others, but the remains of a sec- 
ond layer can be made out in stained sections of the ripe sporan- 
gium (Fig. 280, E). The vascular bundles of the sporophyll 
divide, one branch running to each sporangium. 

Of the two species studied by Bower, E. arvense and E. li- 
moswn, the latter showed more slender and strongly projecting 
sporangia, but otherwise they were alike. E. tclmateia has 
even more massive sporangia than E, arvense. The sporophylls 




Fig. 278. — Longitudinal section of an older sporangium, X260. The nuclei are shown 

in the archesporial cells. 



form a regular cone at the apex of the fertile branch, and are 
arranged in regular whorls, which vary in number in propor- 
tion to the size of the cone. The top of the sporophyll is al- 
ways polygonal in outline, owing to the lateral pressure of its 
neighbours, and very often they are regularly hexagonal, but 
this bears no relation to the number of sporangia, which usually 
exceed in number the angles of the sporophyll. 



Development of the Spores 

The development of the spores in Eqiiisetum, while agree- 
ing in many respects with that of the eusporangiate Ferns, shows 
some peculiarities that are noteworthy, and as this offers one 
of the best cases for studying spore-formation, it was somewhat 



476 MOSSES AND FERNS chap. 

carefully followed in E. telmateia. After the complete num- 
ber of cells has been formed in the archesporium, and before 
the tapetal cells are broken down, the sporogenous cells are di- 
vided into groups which begin to separate from each other. 
With the enlargement of the sporangium and the breaking down 
of the inner tapetal cells these masses become isolated, and are 
very easily removed from the sporangium (Fig. 240, A). 
They usually consist of four cells, which in water swell up some- 
what. In a fresh condition they appear quite colourless, but 
the cytoplasm is densely granular. The nucleus is very large 
and appears quite transparent with one or two distinct nucleoli. 
In microtome sections of about the same age the numerous rod- 
shaped chromosomes were very evident, but their number could 
not be determined. The nucleolus is conspicuous, and on one 
side, in a slight depression in the nuclear membrane were seen, 
in some cases what were taken to be two centrospheres. The 
latter were not always very evident, and the radiations which 
are usually present about centrospheres, were not seen. From 
the later investigations of Osterhout ( i ) upon E. limosum, it 
is probable that the interpretation of these bodies as centro- 
spheres was not warranted, as he failed to find centrospheres in 
that species, and their presence in many other cases, where it 
was supposed they existed, has been disproved. 

Osterhout has also shown that the bipolar spindle, observed 
in E. talmateia is a secondary condition. In E. limosum, he 
found that about the time the spirem-filament had completely 
separated into the individual chromosomes, a change was ob- 
servable in the cytoplasm surrounding the nucleus. Up to this 
time the cytoplasm in material treated with the Flemming triple 
stain shows the characteristic orange or brownish coloration. 
The cytoplasm immediately around the nucleus now stains a vio- 
let color, and is supposed to assume the character of kinoplasm. 
This kinoplasmic zone increases in size, and gradually assumes 
more and more the appearance of a dense net of delicate fibres — 
the future spindle-fibres. These begin to extend outward into 
the orange cytoplasm and converge at numerous points, so as 
to form a number of conical bundles radiating from the nucleus. 
There is thus developed a multi-polar spindle, and as the nuclear 
membrane gradually disappears, the free ends of these spindle 
fibres penetrate into the nuclear cavity and come in contact with 
the chromosomes, which gradually arrange themselves into the 



XII 



EQUISETINE^ 



A77 



characteristic nuclear plate. The separate nuclear spindles 
finally converge more and more, until finally they unite into a 
more or less definite large bipolar spindle with the nuclear plate 
at the equator (Fig. 279, C). Before the final division takes 
place, the sporogenous cells become completely rounded off, 
and are embedded in a mass of nucleated protoplasm (Fig. 
280, A) derived from the tapetal cells, but also in part from 
some of the archesporial cells which do not develop into spores. 
Fig. 279 shows the successive stages in the process. During 




Fig. 279. — ^A, Group of four sporogenous cells of E. telmateia, X400; B, C, first mitosis 
in E. limosum (after Osterhout) ; B, shows the multipolar spindle; D, E, second 
mitosis in E. telmateia. 



the division of the primary nucleus there is an evident cell plate 
formed, but no division wall. During this first division there 
is probably a reduction in the number of the chromosomes, as 
in Osmiinda. At any rate the number is evidently much smaller 
during the metaphases of the second nuclear divisions (Fig. 
279, D). The second divisions are the same as the primary 
one, and the planes of the two nuclear spindles may either be 
parallel or at right angles (Fig. 279, D). In either case the 
resulting nuclei arrange themselves at equal distances from the 



478 



MOSSES AND FERNS 



CHAP. 



centre of the cell, and the connecting filaments are formed be- 
tween them. In the connecting spindles there is formed be- 
tween each pair of nuclei a cell plate, which soon develops into a 
definite cellulose membrane, and the spores separate completely. 
It is probable that the definitive cell-wall is formed in the 
same way as in the spore- formation of other plants (Mottier 
(3), p. ^2). The cell-plate formed at the equator of the spindle 
in the later stages of division, is split into two layers which thus 




B 



m. 



Fig. 280. — A, Group of sporogenous cells, just before the final division into the spores, 
embedded in the nucleated protoplasm formed from the disintegrated tapetum, and 
sterile archesporial cells, X500; B, optical section of young spore, showing the 
three membranes; m, the middle lamella, Xsoo; C, an older spore, showing the 
splitting of the outermost coat to form the elaters, X500; D, surface view of the 
dorsal cells of the wall of a ripe sporangium, X150; E, section of the wall, show- 
ing the remains of the inner layers of cells (0> X250. 



separate completely the two protoplasts. In the space between 
the protoplasts, the new cell-wall is then laid down. 

The young spore has at first a very delicate cellulose mem- 
brane, which thickens, and later has separated from the outside 
the ''middle layer" (Fig. 280, B, m), which in spores placed in 
water lifts itself in folds from the underlying endospore. The 
outer perinium seems to be unquestionably formed through the 
agency of the nucleated protoplasm, in which the young spores 



XII EQUISETINE^ 479 

lie. It is at first a uniform membrane, closely applied to the 
middle coat, but when placed in water it swells up and separates 
completely from the exospore, or remains attached to it at one 
point only, which marks the point of attachment of the elaters in 
the ripe spores. The elaters arise from the epispore by its 
splitting spirally into four bands (Fig. 280, C), due apparently 
to thickening along these bands, leaving thin places between, 
which are finally absorbed. The outside of the elaters becomes 
cuticularised. The ripe spores contain numerous chloroplasts, 
which only are evident in the latest stages of development. In 
E. arvense the formation of the sporangia begins nearly a year 
before the spores are shed, and they are com])letely developed 
during the preceding autumn. The growth of the fertile 
branch and the scattering of the spores take place very soon 
after growth begins in the spring. Whether in cold climates 
E. telmateia behaves the same way I cannot state ; but in Cali- 
fornia, where growth continues all the winter, the development 
of the sporangia is gradual, and the fertile stems grow up and 
scatter the spores as soon as they are ripe. The ripe sporangia 
are oblong sacs, whose wall is composed for the most part of a 
single layer of elongated cells, marked with spiral thickened 
bands upon the dorsal surface and rings upon the ventral cells, 
where the longitudinal slit by which the sporangium opens is 
placed (Fig. 280, D, E). The internodes in the strobilus are 
very little developed, but as the spores ripen there is a slight 
elongation, by which the sporophylls are separated. 

Classification 

Milde ( I ) divides the genus into two, Eqnisctum^ {Equiseta 
phanopora), in which the accessory cells of the stoma are on a 
level with the surface of the epidermis; and Hippochcctc (E. 
crypfopora), in which the stomata are sunk in depressions of the 
epidermis. In the former group are two divisions, those which, 
like E. arvense and E. telmateia, have the fertile and sterile 
branches different, and those where they are alike, e. g., E. linw- 
sum (Fig. 280, A). Some species, e. g., E. pratense, have the 
fertile stems at first colourless, but afterwards forming chloro- 
phyll and developing branches. In Hippochcete, which includes 
among American species E. hiemale, E. rohustum, E. variega- 

- Euequisetum, Sadebeck. 




Fig. 281. — A, Equisetum Umosunt, Xji; B, E. scirpoides, Xi 



xn EQUISETINEJE 481 

him and E. sctrpoides (Fig. 281, B), the aerial branches are all 
similar and often are quite unbranched. The foliar sheaths 
show considerable variation. In the fertile stems of E. teU 
mateia (Fig. 266) they are extremely large and the ribs very 
prominent, but the separate leaves are not all distinct at the 
apex, but the sheath splits into a few very deeply cleft pointed 
lobes. In the sterile shoots, however, and in all the stems of 
most species, the teeth are very distinct and the foliar sheath 
much shorter. The number of teeth varies from three in 
E. sctrpoides, to thirty or forty, or even more, in E. telmateia 
and E. robitstum. In E. silvaticiim the branches produce 
whorls of secondary branchlets. 

Sadebeck (8) recognises 24 species of Equisetum. The 
largest forms occur in tropical America, where some species, 
e. g., E. giganteum, reach a height of 3 to 12 metres, but are 
relatively slender, the stem usually not exceeding two or three 
centimetres in diameter, and requiring support from the shrubs 
and trees among which it grows. E. Schaifneri is described as 
having a stem about two metres in height with a thickness of 
10 centimetres, but with a very large central cavity, so that it 
is not very strong. In some of the larger species, e. g., E. gi- 
ganteum, cones may be borne at the end of the lateral branches, 
as well as at the apex of the main shoot. 

Fossil Equisetinece 

The living genus Equisetum is represented in a fossil condi- 
dition by a number of closely allied forms, perhaps generically 
identical, and usually united under the name Equisetites. Be- 
sides these, there are several types differing materially from 
Equisetum, but nevertheless undoubtedly related to the living 
forms. The most important of these fossil forms are the char- 
acteristic Palaeozoic fossils belonging to the Calamitaceae and 
Sphenophyllacese. A further discussion of these forms will 
be left for a later chapter. 

Acuities of the Equisetinece 

The Equlsetineae, as will be seen from the account of the 
fossil forms, are a very ancient, group, and their relation to the 
other Pteridophytes somewhat problematical. The modern 
31 



482 MOSSES AND FERNS chap. 

forms being so restricted in nurriber and type, offer but partial 
means of comparison ; still a comparison of these with the sim- 
pler Filicinese does indicate some affinity between the two 
groups, although, as might be expected, a very remote one. 
Van Tieghem (6) has shown that the structure and arrange- 
ment of the vascular bundles in the stem of Ophioglossum and 
Equisetum have much in common. As we have seen, the pro- 
thallium is not essentially different in Equisetum and the euspo- 
rangiate Ferns, and the spermatozoids are closely like those of 
the latter, and not at all like those of the Lycopodinese. This 
latter point I believe to be one of great importance. 

If the Equisetineae do come from a common stock with the 
Ferns, they must have branched off at a very remote period, 
long before the latter had become completely differentiated. 
The very different importance relatively of the stem and leaves 
in the two groups points to this, as well as the extremely dis- 
similar character of the sporophylls. The genus Equisetum 
is evidently but a reduced remnant of a once predominant type 
of plants which has been crowded out by the more specialised 
Ferns and Spermatophytes. The presence of heterospory in 
some fossil forms is interesting, but from what we know at 
present it never developed to the same extent as in the other 
groups of Pteridophytes. 



CHAPTER XIII 

LYCOPODINE^ 

The Lycopodineae, though far exceeding in number the species 
of Eqiiisetiim, are inferior in number to the Ferns. Baker (2) 
enumerates 432 species, of which 334 belong to one genus, 
Selaginella, while another, Lycopodmm, has 94. A more re- 
cent enumeration of the two genera (Pfitzer (2), Hieronymus 
( I ) ) indicates a considerably larger number of species, Selagi- 
nella alone possessing approximately 500 species. Like the 
Equisetinese they are abundant in a fossil condition, and it is 
very evident that these ancient forms wxre, many of them, 
enormously larger than their living representatives, and more 
complicated in structure. The living species are mainly trop- 
ical in their range, but Lycopodium has a number of species 
common in northern countries, and a few species of Selaginella, 
e. g., S. rupestris, have a wider range; but the great majority 
of the species are found only in the moist forests of the tropics. 
The gametophyte of the homosporous forms is known best in 
Lycopodium. Our knowledge of it was based mainly upon 
the important researches of Treub (2), but these have been 
added to by Goebel (18) in the case of L. immdaturn, and 
more recently Bruchmann (5) and Lang (i) have succeeded 
in finding prothallia of several European species, and we now 
have a very satisfactory account of all but their earliest stages. 

The gametophyte in its earliest condition, so far as is cer- 
tainly known, develops chlorophyll, and this condition may be 
permanent, e, g., L. cernuum, but other forms have a chloro- 
phylless prdthallium, and are saprophytic in habit, like Ophio- 
glossum. The germination of these forms is at present un- 
known. 

The sporophyte has the axis strongly developed, and the 

483 



484 



MOSSES AND FERNS 



CHAP. 




Fig. 282. Part of a fruiting plant of Lycopodium clavatum, X i 5 B, sporophyll, with 
sporangium (sp) of L, dendroideum, X12; C, cross-section near the base of an 
aerial shoot of L, dendroideum, X 12. 



XIII LYCOPODINEM 4^5 

leaves, though usually numerous, are simple in structure and 
generally small. The genera are all homosporous except 
Selaginella, which is very markedly heterosporous, and has the 
gametophyte very much reduced and projecting but little be- 
yond the spore wall. 

CLASSIFICATION 
Order I. Lycopodiales 

A. Homosporece 

I. Roots always present; sporangia alike, simple, in the 
axils of more or less modified leaves, which may form a distinct 
strobilus, or may be but little different from the ordinary ones 
both in form and position ; prothallia either green or colourless, 
monoecious. 

Family I. Lycopodiace^ 

Genera 2. — (7) Lycopodhim; {2) Phylloglossum 

II. -Roots absent; vegetative leaves much reduced or w^ell 
developed; sporophylls petiolate, bilobed; sporangia pluriloc-' 
ular; gametophyte unknown. 

Family II. Psilotace^ 
Genera 2. — (i) Psilotimi; {2) Tmesipteris 

B. HeterosporecB 

Characters those of Family L, but spores always of two 
kinds. 

Family III. Selaginellace^ 
Genus i. Selaginella 

THE LYCOPODIACE^ 

The Gametophyte 

The Lycopodiacese include the two genera Lyeopodium 
and Phylloglossum, the latter with a single species, P. Drum- 
mondii. The gametophyte is known in a number of species 
of Lyeopodium, and recently (Thomas (i)), has also been 



486 MOSSES AND FERNS chap. 

described for Phylloglossum. The first investigator who suc- 
ceeded in obtaining the germination of the spores was De Bary 
(i), who studied the earhest stages in the germination in L. 
inundatum, but was unable to obtain the later ones. About 
fifteen years later Fankhauser found the old prothallia of L. 
annotinum (i), but our first complete knowledge of the pro- 
thallium and embryo is due to the labours of Treub (2), who 
examined most thoroughly several tropical species of Lyco- 
podkini. Goebel (18) succeeded in finding a number of pro- 
thallia of L. inundatum which correspond very closely to L. 
cernuum, the first species examined by Treub. Other Euro- 
pean species have more recently been investigated by Bruch- 
mann ( 5 ) and Lang ( i ) . 

The germination of the spores in L. cernuum and L. in- 
undatum is much like that of the homosporous eusporangiate 
Ferns. The tetrahedral spores contain no chlorophyll, but it 
develops before the first division wall is formed. This may 
be either vertical or horizontal, or more or less inclined. The 
two primary cells are nearly equal in size, but one of them ap- 
pears to normally remain undivided. The other enlarges and 
becomes divided by an oblique wall (Fig. 283, A), and func- 
tions for some time as an apical cell, from which segments are 
cut off alternately right and left. Usually each segment is then 
divided by a periclinal wall into a central and a peripheral cell. 
Up to this point the germination of L. cernuum corresponds 
exactly with De Bary's observations upon L. inundatum. The 
ovoid body formed at first Treub calls the "primary tubercle,'^ 
and this does not develop directly into the complete prothal- 
lium, but the apical cell ceases to form two rows of segments 
and elongates so as to produce a filament in which for a time 
only transverse walls are formed (Fig. 283, B). The base 
of this filamentous appendage, however, later develops longi- 
tudinal walls and forms a thickened cylindrical mass, which 
is the beginning of the prothallium body. Sometimes, but not 
usually, a second filamentous outgrowth is formed from the 
primary tubercle, which may produce a second prothallial body. 

The growth of the prothallium proper does not seem to 
show a definite meristem, but at the summit are produced a 
number of leaf-like lobes which seem to arise in acropetal suc- 
cession, and the growth may be considered, in a general way 
at least, as apical. The individual lobes are usually two cells 



XIII 



LYCOPODINEM 



487 



thick, and like those of EquiseHmi show a definite two-sided 
apical cell. This apical growth later disappears and all trace 
of it is lost in the older lobes. Rhizoids are produced only 
in small numbers from the cylindrical prothallium body, and 
are usually entirely absent from the primary tubercle, whose 
peripheral cells are always occupied by an endophytic fungus 
which Treub refers probably to the genus Pythiiim. We have 
seen that similar fungus mycelia occur in the chlorophylless 




Fig. 283. — A, B, very young prothallia of Lycopodium cernuum. A, X250; B, X200. 
P, Primary tubercle; C, an older prothallium of the same species with the first 
antheridium ((^), X75; D, a fully-developed prothallium (pr) with the young 
sporophyte attached, X12; pc, protocorm; R, primary root; E, section through an 
antheridial branch of the prothallium of L. phlegmaria, showing antheridia 
{(^) in different stages of development; par, a paraphysis, X180; F, surface view 
of the top of an antheridium of the same species; o, opercular cell, X180; G, a 
spermatozoid, X410; H, section of the archegonium of the same species, X 180 
(all the figures after Treub). 



prothallium of Botrychium, and Goebel found the same in L. 
inundatum. While in the primary tubercle the fungus occu- 
pies the lumen of the cells, as it penetrates into the body of the 
prothallium it confines itself mainly to the intercellular spaces, 
where its growth causes more or less displacement of the cells. 
It does not, however, seem to penetrate into the meristematic 
tissues at the summit. 

The fully-grown prothallium of L. cernuum is a small up- 



488 MOSSES AND FERNS chap. 

right cylindrical body, seldom, apparently, exceeding about 
two mm. in height. The base is more or less completely 
buried in the ground, and contains but little chlorophyll. The 
summit is surrounded by the lobes already spoken of, and these 
have somewhat the appearance of leaves crowning a short stem. 
The whole structure of the prothallium recalls in some respects 
that of Eqiiisetum, but differs in the important particular that 
it is radiallv constructed, and is not dorsi-ventral. 

Besides the type of prothallium found in L. cernuum, with 
which L. inundatum closely agrees, Treub has also studied the 
very different prothallium of L. phlegmaria, and others of sim- 
ilar habit. These are only known in their mature condition, in 
which they are saprophytes, growing in the outer decayed lay- 
ers of bark upon the trunks of trees. In this condition they 
are extremely slender branched structures, totally different 
from those of L. cernuum, both in form and in the complete 
absence of chlorophyll. Like the prothallia of many Hymeno- 
phyllacese, they multiply by special gemmae and apparently may 
live for a long time. Like those of L. cernuum they are always 
infected by an endophytic fungus. 

Bruchmann (4) finds that there is a good deal of differ- 
ence among the European species. L. clavatum (Fig. 284, A) 
and L. annotinum represent one type. The gametophyte is 
subterranean, and in appearance not very different from that 
of Botrychkim, although its manner of growth is of an entirely 
different type. In the earliest stages observed, it was an up- 
right, top-shaped body, the upper surface of which was some- 
what depressed below the margin, which forms an elevated rim 
about the central area. There is no proper apical growth, but 
a zone of cells between the rim and the central area is meriste- 
matic, and to the growth of this zone the future development of 
the gametophyte is due. The whole of the central area is de- 
voted to the formation of the reproductive organs, and consti- 
tutes the ''generative tissue," and like the similar tissue in Bo- 
try cliiuni, its cells are almost destitute of granular contents. 
Outside the colourless generative tissue is a layer of dense stor- 
age-cells, and outside of these a layer of tissue in which is an 
endophytic fungus. Unicellular rhizoids occur in consider- 
able numbers upon the under surface. 

The gametophyte of L. complanatum (Fig. 284, C) is also 
subterranean, but quite different in form from that of L. clav- 



XIII 



LYCOPODINEJE 



489 



atiim, although the essential structure is much the same. It is 
a fusiform structure, with a terminal mass of short, irregular 
lobes covered with the reproductive organs. Between the ter- 
minal generative portion and the sterile fusiform body of the 
prothallium, there is a meristematic zone, corresponding to that 
in L. clarjatum. The oldest reproductive organs are at the 
centre of the generative area, the youngest are next the zone of 
meristematic tissue. 

L. Selago closely resembles L. phlegmaria in the structure 
of the gametophyte, and there are similar paraphyses formed 
among the reproductive organs. 

L. inimdatum, as was pre- 
viously shown by Goebel,. be- 
longs to the type of L. ccr- 
nuiim, and Phylloglossiun 
(Thomas (i)) seems to be 
very much like L. cernuum, 
in the structure of the game- 
tophyte. 

The gametophytes of all 
species are normally dioe- 
cious, but the antheridia 
usually develop first. 



The Sexual Organs 




Fig. 284. — A, Lycopodium clavatum, gameto- 
phyte, X3; B, L. annotinum, old game- 
tophyte, with young sporophytes, sp, at- 
tached, X3; C, gametophyte of L. com- 
planatum, X3 (after Bruchmann). 



The sexual organs of all 
investigated species of Lyco- 
podiuni are very similar, and 
resemble those of the eusporangiate Ferns and Equisetum. 
As in these forms the antheridium mother cell divides first by a 
periclinal w^all into an outer and inner cell, the latter giving 
rise immediately to the sperm cells. In the outer cell the divi- 
sions are much like those in Marattia, but the opercular cell 
does not become detached as in these, but is broken through 
as in the Polypodiaceae. In L. phlegmaria the outer w^all is 
often in places double, as not unfrequently is the case in the 
Ophioglossacese. The spermatozoids are almost straight ob- 
long bodies with two cilia, like those of the Bryophytes (Fig. 
283, G). The vesicle, which usually remains attached to the 
spermatozoids of most Archegoniates, here is almost always 



490 MOSSES AND FERNS chap. 

free and often remains within the sperm cell after the escape 
of the spermatozoids. 

The archegonium in most species of Lycopodium differs a 
good deal from that of the other Pteridophytes, especially in 
the large number of neck canal cells that are usually found. 
The cells of the axial row may be as many as ten in L. annoti- 
num, and in L. cornplanatum Miss Lyon (3) found 14-16 cells, 
which in some cases had two nuclei in each cell, a condition 
which is also found in L. phlegmaria. L. cernuum, however, 
according to Treub, has but a single neck canal cell. 

In the remarkably large number of canal cells, as well as 
in the occasional development of five instead of four outer cell- 
rows in the neck (Bruchmann (4), p. 34), Lycopodium un- 
doubtedly resembles more nearly the typical Bryophytes than 
does any other of the Pteridophytes. 

The Embryo {Treub (2); Bruchmann (4)) 

Treub has traced the development of the embryo in L. 
phlegmaria through all its stages, and has shown that L. cer- 
nuum corresponds closely to it, and Goebel's investigations 
upon L. inundatum show that this species does not differ essen- 
tially from the others. The first division in the embryo is 
transverse, and of the two primary cells the one next the arche- 
gonium remains undivided, or divides once by a transverse 
wall and forms the suspensor, which is characteristic of all in- 
vestigated Lycopodinese, while the lower cell alone gives rise 
to the embryo proper. In the embryonal cell the first wall is 
a somewhat oblique transverse one, which divides it into un- 
equal cells. In the larger of these a wall forms at right angles 
to the primary wall (Fig. 285, A), and this is soon followed 
in the smaller cell by a similar one, so that the embryo is di- 
vided into quadrants. Of these the two lower form the foot, 
while of the upper ones in L. phlegmaria, the one formed from 
the larger of the two primary cells (moitie convexe of Treub) 
produces the cotyledon, the other the stem apex. The primary 
root, which in Lycopodium arises very late, originates from 
the same quadrant as the cotyledon. 

In L. cernuum, while the early divisions correspond exactly 
with those of L. phlegmaria, the further development of the 
embryo shows some noteworthy differences. As in that 



XIII 



LYCOPODINE^ 



491 



Species, the two lower quadrants form the foot, which here 
remains completely buried within the prothallium. From the 
upper part of the embryo is next developed what Treub calls 
the "protocorm." This is a tuber-like organ (Fig. 283, D, 

A. 




Fig. 285. — Embryogeny of Lycopodium phlegmaria (after Treub). st. Stem; cot, 
cotyledon; susp, suspensor. A, X315; B, X235; C, X235; D, Xi7S- 



pc), from which the leaves and stem apex are subsequently 
developed. The cotyledon arises from the summit of the pro- 
tocorm, and is followed by a number of secondary leaves which 



492 MOSSES AND FERNS chap. 

form successively from a group of meristematic cells, which 
usually develop into the permanent apex of the stem. About 
the time that the stem apex becomes recognisable as such, the 
first root appears as a surface outgrowth of the protocorm, 
and strictly exogenous in origin. Not infrequently the end 
of the primary root gives rise to a tubercle similar to the proto- 
corm. 

An interesting case was seen by Treub, where, apparently 
by a longitudinal division of the young embryo, two embryos 
were formed, much as is normally the case in some Gymno- 
sperms. 

On comparing the two types of embryo found in L. phleg- 
maria and L. cermmm, the main differences are the almost 
complete absence of the protocorm and greater development of 
the suspensor in the former. L. inundatum, as might be ex- 
pected, corresponds closely in the structure of the young sporo- 
phyte to L. cernimm. 

Corresponding with the late appearance of the roots is the 
late development of the vascular bundles, which, according to 
Treub, are often quite absent from the cotyledon and even 
occasionally from the second leaf. The protocorm of L. cer- 
nuum and L. inundatum Treub regards as the remains of a 
primitive structure originally possessed by the Pteridophytes, 
which replaced the definite leafy axis found in the more special- 
ised existing forms. 

Phylloglossum, which has sometimes been regarded as the 
most primitive of existing Pteridophytes, resembles closely the 
young sporophyte of Lye op odium cernuum. 

Bruchmann states ((4), p. 38) that the fertilised egg en- 
larges very much before the first division wall is formed, differ- 
ing in this respect from Selaginella, and more resembling Ma- 
rattia or Botrychium. The first division is transverse. The 
larger of the two cells, lying next the archegonium-neck, forms 
the suspensor, and the smaller one develops into the embryo 
itself. 

Both L. clavatum and L. annotinum differ from the species 
studied by Treub in the late development of the leaves (Bruch- 
mann (4), p. 46). Moreover, in these species there are two 
opposite cotyledons as in Selaginella. 

The development of the young sporophyte is extraordi- 
narily slow, and Bruchmann states that it sometimes does not 



XIII 



LYCOPODINE^ 



493 



appear above the surface of the earth until several years have 
elapsed. The leaves developed up(jn tliese subterranean shoots 
are rudimentary. Sometimes more than one sporophyte is 
borne by the prothallium (Fig. 284, B). The differentiation 
of the vascular cylinder begins about the time that tlie root 
breaks through the prothallial tissue. The hypocotyledonary 
part of the stele is diarch, but higher up four or five protoxylem 
groups are developed. 




Fig. 286. — A, Lycopodium pachystachyon, X M ; B, L. voluhile, showing the two forms 

of leaves, X2%. 



The Adult Sporophyte 

In all species of Lycopodium the sporophyte possesses an 
extensively branched stem, which may be upright, as in L. 
cernuum, or extensively creeping, as in L. clavatum and other 
species, where the main axis is a more or less completely sub- 
terranean rhizome with upright secondary branches. In the 
tropics some species are epiphytes. The leaves are always 
simple, and of small size. Each leaf has a single median vas- 
cular bundle, which does not extend to the apex. The ar- 
rangement of the leaves is usually spiral, and they are uni- 
formly distributed about the stem, and all alike ; but in a few 
species, e. g., L. complanatiim and L. z'olubile, they are of two 



494 



MOSSES AND FERNS 



CHAP. 



kinds and arranged in four rows, as in most species of Selagi- 
nella. The branching of the stem is either dichotomous or 
monopodial. The roots, which are borne in acropetal succes- 
sion (Bruchmann found also in L. inundatum adventive roots), 
branch dichotomously, hke those of Isoetes. The sporangia 
are borne singly, in the axils of the sporophylls, which may 
differ scarcely at all from the ordinary leaves (L. selago, L. 
hicidulum), (Fig. 287), or the sporophylls are different in 
form and size from the other leaves and form distinct strobili, 





Fig. 287. — Lycopodium selago. A, Longitudinal section of the stem apex, X120; F, F, 
young leaves; i, i, initial cells; PI, plerome; B, surface view of the stem apex, 
showing the group of initial cells, X260; C, longitudinal section of the root- tip; d, 
dermatogen; Pb, periblem; PI, plerome; Cal, calyptrogen; h, h, root-hair initials, 
X 120 (all the figures after Strasburger). 



which are often borne at the end of almost leafless branches 
(Fig. 282). 

None of the investigated species of Lycopodium show a 
definite initial cell at the apex of the stem, and Treub ( (2), V) 
was unable to determine positively whether such a one exists in 
the embryo. In L. phlegmaria he describes and figures, em- 
bryos, where a single prismatic apical cell is apparently pres- 
ent, but in others the presence of such a cell was doubtful, and 
in L. cernmmi in no case did he find any evidence of a single 
initial. 

The vegetative cone of the mature sporophyte is usually 



XIII LYCOPODINEJE 495 

broad (Fig. 287) and only slightly convex. Its centre is occu- 
pied by a group of similar initial cells, which in L. sclago, 
according to Strasburger ((10), p. 240), usually show two 
initials in longitudinal section (Fig. 287, i). From these in- 
itials are cut off lateral segments which, by further periclinal 
and anticlinal walls, produce the epidermis and cortex, and sec- 
ondarily the leaves. Periclinal walls also are formed from 
time to time in the initial cells, by which basal segments are 
cut off, wiiich produce the large central plerome cylinder. 

The leaves arise as conical outgrowths near the stem apex, 
and owe their origin to the three or four outer cell layers of the 
growing point. The separation of the epidermis does not oc- 
cur until the leaf has formed a conspicuous conical protuber- 
ance. The differentiation of the procambium in the young 
leaf begins early, and the strand joins the central procambial 
cylinder of the stem, which, however, is quite independent 
of the leaf-traces. Each young leaf-trace joins an older one 
at the point of junction with the stem cylinder, and thus the 
complete stem possesses two systems of vascular bundles, the 
strictly cauline central cylinder, and the system of common 
bundles formed by the united leaf-traces. 

The first elements of the vascular bundles to become recog- 
nisable are spiral tracheids, both in the stem and leaves, and 
these are followed in the former by the much wider scalari- 
form tracheids that occupy the central part of the tracheary 
plates in the fully-developed bundles. 

The fully-developed central cylinder of the stem (Russow 
(i),p. 128; De Bary (3), p. 281; Strasburger (11), vol. iii., 
p. 458; Strasburger, /. c, p. 460; Van Tieghem (5), p. 553) 
is undoubtedly to be considered as a group of confluent vascu- 
lar bundles or as gamostelic. The oval or nearly circular cross- 
section (Fig. 288, A) is sharply separated from the surround- 
ing ground tissue by a clearly-marked endodermis, within 
which is a pericycle which may be only one cell thick, but is 
usually several-layered. According to Strasburger this peri- 
cycle does not properly belong to the central cylinder, but is 
of cortical origin.' The cutinised band ("radial folding") of 
the endodermal cells is only observable in the younger stages, 
as later the whole wall of the endodermal cells become cutin- 
ised. This cutinisation extends also through a number of the 
succeeding cortical layers. The rest of the cortical region is 



496 



MOSSES AND FERNS 



CHAP. 



in most species occupied by elongated sclerenchyma cells, with 
no intercellular spaces. 

The central vascular cylinder contains, as is well known, 
several, usually transversely placed, tracheary plates, alter- 
nating with phloem masses, and surrounding these a varying 
amount of parenchyma. In upright species the tracheary 
plates are often more or less completely confluent, and in cross- 
section have a somewhat star-shaped outline. In the dorsi- 
ventral stems the tracheary plates are quite separate and per- 
fectly transverse in position. Their outer angles are occupied 







G 


^ 




« 




(S> , 


^'. ^ 




• *^ 


.S"^ 


•ttO" 


C^ 


■»<=» 


P> 


" - -a* 




» «^ 




.T'-* <Ek 




m ^ ^ 








«> 




■^ i 




— 1 




«ak 1 


1 


I 



Fig. 288. — A-D, Lycopodium volubile; A, transverse section of the stem, X18; /, leaf- 
base; B, tissues of the central part of the stem, X about 200; C, sieve-tube show- 
ing lateral sieve-plates, X about 600; D, section of the wall of a sieve-tube; E, 
section of the leaf of L. lucidulum, X35. 



by the small primary spiral or annular tracheids, from which 
the centripetal formation of the large scalariform elements 
proceeds exactly as in the leptosporangiate Ferns. The mass 
of tracheary tissue is compact, and contains no parenchyma- 
tous elements. According to Strasburger the oblique end 
walls of the large tracheids show the same elongated pits as the 
lateral walls, but in no cases could any communication between 
adjacent tracheids be demonstrated. Each tracheary mass is 



XIII LYCOPODINE^ 



497 



surrounded by a single layer of parenchyma, whose inner cell 
walls show bordered pits like those of the adjacent traclieids. 

The phloem masses are, in the arrangement and develop- 
ment of the parts, very like the xylem, and the formation of 
the sieve-tubes begins at the outer angles and proceeds centrip- 
etally. The large sieve-tujjes in L. voliibile (Fig. 288, C) are 
conspicuous, appearing nearly empty, and with delicate, colour- 
less walls. Upon their lateral faces are numerous sieve-plates, 
which in the smaller species are not easily demonstrated. 

Where the branching is monopodial, the young branches 
arise laterally close to the growing point, but without any re- 
lation to the leaves. Where, however, as in L. selago ( Stras- 
burger (10), p. 242), there is a genuine dichotomy, it is in- 
augurated by an increase in the number of initial cells, which 
is then followed by a forking of the apex of the plerome cyl- 
inder, and the two resulting branches are exactly alike. Inter- 
mediate conditions betw^een a perfect dichotomy and true mon- 
opodial branching occur. In these there is a true dichotomy, 
but one branch is stronger than the other, and continues as the 
main axis, w^hile the weaker one is pushed to one side and looks 
like a lateral shoot. Bruchmann has described certain *'pseu- 
do-adventive" buds, w^hich are young branches arrested in their 
development at a very early stage, which may later develop. 
Strasburger (7) has found adventive buds in L. aloifolium, L. 
verticillaHim, L. taxi folium, and L. reflexiim, which possibly 
may be of the same nature. 

The Leaf 

The leaves of all species of Lycopodmm are relatively small, 
and are usually lanceolate in outline with broad sessile base. 
The margins of the leaves are often serrate, and in all cases 
the leaf is traversed by a simple midrib, which, as already 
stated, does not reach to the apex. Their arrangement varies, 
even in the same species, and upon the same shoot. Thus in 
L. alpiniim (Hegelmaier (i), p. 815) the leaves are regularly 
arranged in pairs which arise simultaneously; in L. selago 
they are usually in true whorls of four or five. The latter, 
however, often shows a spiral arrangement of the leaves, with 
a divergence of two-ninths, less often two-sevenths. In other 
species, e. g., L. complanatum, L. vohihile (Fig. 286, B), the 
32 



498 MOSSES AND FERNS chap. 

leaves are dimorphous and arranged in four ranks, like those 
of most species of Selaginella. 

The structure of the vascular bundle of the leaf is simple. 
It is concentric in structure, with the central part composed 
of a small number of spiral and annular tracheids, and the 
peripheral portion made up of parenchyma, with a circle of 
scattered narrow sieve-tubes. A definite endodermis cannot 
be demonstrated. In the species with the leaves all alike both 
surfaces bear stomata, but in those with decussate leaves the 
greater part of the upper surface is destitute of them. 

The Root 

The roots of Lycopodium arise, as in other Pteridophytes, 
in acropetal succession, but with no relation to the position of 
the other organs. According to Bruchmann adventive roots 
may arise in L. inundatum, but they have not been observed 
in other forms. L. selago (Strasburger (lo), p. 259) may 
serve to show the characters of the root in the genus. The 
meristem of the apex is clearly differentiated into the initials 
of the different primary tissues (Fig. 287, G). The dermat- 
ogen (d) completely covers the apex of the growing point as 
a single layer. The periblem (pb) is three cells thick; the 
plerome (pi) terminates in a group of special initials. As in 
the stem, the plerome alone forms the central cylinder, the peri- 
blem giving rise only to the cortex, and the structure of the 
mature root corresponds closely to that of the stem, except for 
the presence of the root-cap, which has its own initial group of 
cells (calyptrogen, cal). From the older dermatogen cells are 
derived, by special walls, the mother cells of the root-hairs (h). 

Van Tieghem ((5), p. 553) states that the secondary roots 
arise from the pericycle instead of from the endodermis, as in 
other Pteridophytes; but Strasburger claims that the so-called 
pericycle of Lycopodium is really cortical, and does not belong 
properly to the central cylinder, so that this difference is only 
apparent. The endodermis itself is not readily recognisable 
on account of the complete cutinisation of the walls. 

The origin of the root-hairs is somewhat peculiar. From 
the base of each dermatogen cell a wedge-shaped cell is cut off 
(Fig. 287, C, h), and this afterwards is divided into two sim- 
ilar cells, each of which grows out into a unicellular hair. 
Thus the root-hairs are found in pairs. 



XIII 



LYCOPODINEJE 



499 



The roots always normally branch dichotomously, as in 
Isoetes, and the success! v^e divisions usually are in planes at 
right angles to each other. As in Isoetes, tlie process is in- 
augurated by a broadening of the apex of the root, which is 
followed by a forking of the plerome and a subsequent division 
of the other histogenic tissues. 

The structure of the mature root (Russow (i)) in L. 
clavatum, L. alpinum, and 
most species examined, is 
much like the stem. The 
hexarch to decarch fibrovas- 
cular cylinder is radial in 
structure, the xylem plates 
often united at the centre, so 
that in cross-section they 
present a more or less regu- 
lar stellate form. In L. 
selago and L. inundatum, 
according to Russow, the 
xylem is diarch and the two 
masses united into a single 
one, which is crescent-shaped 
in section, with the phloem 
occupying the space between 
the extremities. As in the 
stem the primary tracheids 
are narrow annular and 
spiral ones, and the large 
secondary ones scalariform. 

GemmcB 




Fig. 289. — A, End of a shoot of Lyco- 
podium lucidiihim, with gemmae 
(fe) and sporangia {sp), X2; B, a 
single bulblet, X4; C, germinating 
bulblet of L. selago (after Cramer), 
X4; y, the primary root. 



Special bulblets or gem- 
mae are formed regularly in 
a number of species of Ly 
copodium, and have been 
the subject of several special 

investigations (Cramer (i); Hegelmaier (i); Strasburger 
(7)). These in L. lucidulnm (Fig. 289, A, k) are flattened, 
heart-shaped structures composed of several thickened fleshy 
leaves, and formed apparently in the axils of somewhat modi- 



500 MOSSES AND FERNS chap. 

fied stem leaves, from which they readily separate when fully 
grown. The axillary origin of the bulblets is only apparent; 
they are really, so far as can be determined, similar in origin 
to the ordinary branches, and formed without any relation to 
the leaves. Before the bulblet becomes detached, the rudiment 
of a root can be made out at the base, and as soon as it falls off 
and comes in contact w^ith the earth the root begins to grow and 
fastens the bulblet to the ground (Fig. 289, C). The axis of 
the bulblet, which at first is very short, rapidly elongates, and 
the leaves formed up it have the characters of the ordinary 
ones. As the leafy axis develops the fleshy leaves of the bulb- 
let lose their chlorophyll completely and finally decay. 

Hegelmaier describes mucilage ducts in the stem and leaves 
of L. inundatum and some other species, which are not unlike 
those found in Angiopteris. 

The Sporangium 

The most recent and accurate account of the structure and 
development of the sporangia of the Lycopodinese is that given 
by Professor Bower in his memoir upon this subject (15). 
His investigations include a number of species of Lycopodium, 
and the following account is taken mainly from his memoir. 
The results of his investigations show that there is much more 
variety shown than was before supposed, both in the form of 
the sporangium itself and in the mode of origin and number of 
the archesporial cells. 

In L. selago the sporangium originates upon the upper 
surface of the sporophyll close to its base, and in radial section 
the young sporangium appears to originate from a single cell ; 
but this is really only one of a transverse row of cells, all of 
which participate in its formation. Each cell of this primary 
row divides first into a large central cell (Fig. 290, C, x) and 
(in radial section) two peripheral ones. The central cell next 
by successive periclinals forms a row of three cells, of which 
the middle one is the archesporium, which, judging only from 
radial sections, seems to consist only of a single cell ; but com- 
paring with the radial section a tangential one, it is seen that 
the archesporium really consists of a row of similar cells (Fig. 
290, F). The growth in the upper part of the sporangium is 
stronger than beloW; so that a distinct, although short stalk is 



XIII 



LYC0P0DINE2E 



501 




Fig. 290. — A, Plant of Phylloglossum Drummondn, X about 3 (after Bertrand). sp. 
Sporangia; R, roots; T^, protocorm; T^, secondary protocorm; B, longitudinal sec- 
tion of the young strobilus of the same, showing the initial cell (i), young leaves 
(/', /"), and young sporangium (jp), X240; C-E, young sporangia of Lycopodium 
selago, radial sections, X225; F, tangential section of the same; G, radial section 
of young sporangium of L. clavatum (Figs. B-G after Bower). 



502 MOSSES AND FERNS chap. 

formed. The archesporial cells rapidly divide, but show little 
regularity in the divisions. All of the resulting cells separate 
and produce four spores in the usual manner. The wall of the 
mature sporangium consists regularly of three layers of cells, 
of which the innermost is the tapetum. The tapetum bound- 
ing the lower part of the archesporium is derived from the 
cushion-like group of cells below it, to which Bower gives the 
name ''sub-archesporial pad." The tapetum does not become 
disorganised, as in most Ferns and Equisetum, but remains 
as part of the sporangium wall. The fully-grown sporangium, 
as in all species of Lycopodium, is kidney-shaped. 

Among the numerous other species investigated by Profes- 
sor Bower, L. clavatum represents the type most widely re- 
moved from L. selago. The differences between the two are 
summarised by Professor Bower as follows : 

"i. The sporangium is similar in position and in general 
form to that of L. selago, but its body is more strongly curved. 

"2. The archesporium here consists of three rows of cells, 
each row being composed of a large number (about twelve) 
of cells ; thus the extent of the archesporium is much greater 
than in L. selago, occasional additions to it seem to be made 
by cells cut off periclinally from the superficial cell at an early 
stage. 

"3. The tapetum is similar in origin to that in L. selago. 

"4. The sub-archesporial pad is much more developed, and 
is at times extended as processes of tissue which penetrate the 
sporogenous mass for a short distance. 

"5. The stalk of the sporangium is much shorter and 
thicker than in L. selago. 

"6. Arrested sporangia are frequently present, and may be 
found either at the base or apex of the strobilus. 

"7. L. inundatum may be looked upon as an intermediate 
link between the type of sporangium of L. selago and that of 
L. clavatum, both as regards form of the sporangium and com- 
plexity of the archesporium." 

Phylloglossum 

The other genus of the Lycopodiacese contains but the single 
species P. Drummondii, from Australia and New Zealand. 
This curious and interesting little plant has been carefully in- 



XIII LYCOPODINE^ 503 

vestigated by Bower (5) and Bertrand (3), and the former 
regards it as the most primitive in structure of all the living 
Pteridophytes. 

The sporophyte resembles in an extraordinary degree the 
young sporophyte of Lycopodiiim, especially L. cernmun. It 
grov^^s from a small tubercle (protocorm), which is regarded as 
homologous with the same structure in the embryo of Lyco- 
podiiim. This protocorm in small plants produces only sterile 
leaves — from four to twenty — and a small number of roots, 
often only a single one. In more vigorous plants a smaller 
number of sterile leaves is formed, but the apex of the proto- 
corm grows into an elongated axis, bearing a single small stro- 
bilus at the apex (Fig. 290, A). The structure of the latter 
is essentially as in Lycopodium. The roots are produced exog- 
enously, as in the Lycopodium embryo, and are in structure 
much the same. All of the tissues are very simple, and none 
of the organs show a single apical cell, except possibly the apex 
of the strobilus, where such a single initial seems to be some- 
times present (Fig. 290, B, /). At the end of the growing 
season a new protocorm is formed. This arises directly from 
the apex of the old one, where no strobilus is developed, but in 
the latter case grows out upon a sort of peduncle from near the 
base of one of the leaves. The development of the sporangia 
is essentially the same as in L. selago (Fig. 290, B). 

The anatomy of the vegetative organs has been carefully 
studied by Bertrand, and corresponds closely to that of Lyco- 
podium, but the tissues are simpler. In the axis which bears 
the strobilus there are about six xylem masses arranged in a 
circle, but there is no definite endodermis limiting the central 
cylinder. The root-bundle is diarch. 

Recently the gametophyte of Phylloglossiim has been dis- 
covered and described by Thomas ( i ) . In its main features 
it agrees with that of Lycopodium cermmm, having abundant 
chlorophyll, and having much the same general structure. The 
sexual organs and embryo also resemble those of L. cernuum. 

Bertrand states that M. L. Crie found that the spores ger- 
minated readily, and produced a colourless prothallium like 
that of the Ophioglossacese, both in form and in the structure 
of the sexual organs, but that the spermatozoids are biciliate. 

These observations do not agree with the results of 
Thomas's investigations. The latter observer thinks that per- 



504 MOSSES AND FERNS chap. 

haps Crie may have obtained only the early stages of the pri- 
mary tubercle. The differences between Phylloglossum and 
Lycopodium do not seem sufficient to warrant the establishment 
of a separate family, the Phylloglossese, as Bertrand proposes. 

The Psilotace^ {Pritzel (i)) 

The Psilotaceae include the two evidently related genera 
Psilotum and Tmesipteris, the former with two extremely vari- 
able species (Baker ( i ) ) , the latter with but a single one. All 
the species are tropical or sub-tropical, Psilotum being found in 
all the warmer parts of the world ; but Tmesipteris is confined 
to Australia, New Zealand, and parts of Polynesia. The pro- 
thallium is quite unknowm in both genera, but the development 
and anatomy of the sporophyte of both are now pretty well 
known. The sporophyte (Bertrand (i, 2); Bower (15); 
Solms-Laubach ( i ) ) , which in its mature condition is quite 
destitute of roots, grows either vipon earth rich in humus 
, (Psilotum triquetrum), and is evidently more or less sapro- 
phytic, or it may be an epiphyte. Tmesipteris grows upon the 
trunks of tree-Ferns, and Bertrand states that it is a true para- 
site, which, however, like Viscum or Phorodendron, has not 
entirely lost its chlorophyll. The plant always consists of two 
parts, a lower portion consisting of branched root-like rhizomes, 
which take the place of roots, and aerial green branches which 
ramify dichotomously. The branching is especially marked in 
Psilotum, much less so in Tmesipteris. The leaves are small 
and scale-like in Psilotum, larger and lanceolate in Tmesipteris. 
The sporangia (or synangia) are bilocular in the latter, trilocu- 
lar in Psilotum and in both cases borne upon a smaller bilobed 
sporophyll. 

The development of the sporophyte has been carefully 
studied by Solms-Laubach (i), who discovered that it multi- 
plied rapidly by means of small gemmae (Fig- 292, k) produced 
in great numbers upon the subterranean shoots. These buds or 
bulblets are small oval bodies, but one cell in thickness, and 
showing usually a definite tw^o-sided apical cell. Their cells 
are filled with starch, and they sometimes remain a long time 
dormant. These buds may produce others, but usually from 
each one is produced one, or sometimes more, elongated shoots, 
which develop into subterranean branches like those from 



XIII 



LYCOPODINEjE 



505 



which the bud was originally produced. The young plant 
arising from the gemma is at first composed of uniform paren- 
chyma, but in the later formed portions a simple vascular bundle 
is finally developed. No definite apical cell can be detected in 



-57-U 




Fig. 291.— Part of a vigorous plant of Psilotum triquetrum, about %; u, u, Sub- 
terranean shoots; a, a, the bases of aerial branches; sy, synangia; B, branch with 
two mature synangia, slightly enlarged; C, a single opened synangium, showing 
the two lobes of the sporophyll below it (after Bertrand). 



the earlier stages, but later each branch of the rhizome shows 
a pyramidal initial cell, much like that in the Ferns, but less 
regular in its divisions, and it is not possible to trace back all 
the tissues with certainty to this single cell. The branching is 
a true dichotomy, but is not brought about by the division of 



So6 



MOSSES AND FERNS 



CHAP. 



the original apical cell, but this becomes obliterated previous 
to the formation of the two branches, and two new initial cells 
are formed quite independently of it. 

The tissues of the Psilotaceae are quite simple (Russow ( i), 
Pritzel ( I ) , Ford ( i ) ) . The most recent account is by Miss 
Ford, who has made a very complete study of the tissues of 
Psilo turn triquetnim. 

The surface of the aerial shoot is strongly ribbed (Fig. 293, 
A) in the stouter portions, but nearly triangular in section 




Fig. 292 — Psilotum triquetrum. A, Fragment of a subterranean shoot with a 
young gemma (k) , X120; B, longitudinal section of the apex of a subterranean 
shoot, X185; C, transverse section of the apex of a subterranean shoot in the act 
of forking, x, x, the apical cells of the two branches, Xi8s (all figures after 
Solms-Laubach) . 



nearer the apex. Within the epidermis, in which are numerous 
stomata, there is a zone of outer cortical cells, containing nu- 
merous chloroplasts, and constituting the principal assimilating 
tissue. The cells of this zone are irregular in outline, with 
numerous intercellular spaces, like the mesophyll of many 
leaves. Inside this assimilative cortex is a zone of scleren- 
chyma forming the principal mechanical tissue of the shoot. 
Within this zone is a mass of thin- walled parenchyma, bounded. 



XIII 



lYCOPODlNEM 



so? 



internally by the endodermis which limits the central cylinder. 
Miss Ford finds that with proper treatment, the endodermis 
can be readily differentiated, although ordinarily its presence 
is not evident. 

The central cylinder, or stele, has its axis composed of a 
mass of sclerenchyma about which the radiating xylem-masses 
form a more or less regular star-shaped mass, when seen in 
transverse section. The number of xylem masses varies from 
3 to lo. The protoxylem, composed as usual of narrow spiral 
tracheids, occupies the points of the star-shaped section, the 
larger secondary tracheids being developed centripetally. The 
latter are scalariform. The phloem is very poorly differenti- 
ated, and its boundaries are impossible to determine exactly. 
Larger elements, probably representing sieve-tubes, are present 




Fig. 293. — ^A, Section of the stem of Psilotum triquetrum, X^^o; B, part of the central 
cylinder, X150; C, section of the stem of Tmesipteris tannensis, X20; D, part of 
the central cylinder, X150. 



but neither well-defined sieve-plates nor callus could be dem- 
onstrated. Between the endodermis and protoxylem are sev- 
eral layers of pericycle cells. In Psilotum the leaves have no 
vascular bundle; in Tmesipteris a single bundle traverses the 
leaf, as in Lycopodiiim. 

The structure of the stem in Tmesipteris (Fig. 293, C) is 
much like that of Psilotum, but is simpler. There are 3 to 5 
xylem-masses which are much less symmetrically arranged 
than in Psilotum. The leaves, however, possess a w'ell-devel- 



5o8 



MOSSES AND FERNS 



CHAP. 



Oped vascular bundle, which is continued into the stem as a 
leaf-trace, and joins the axial cylinder. 

The Sporangium (Bower (13)) 

There has been much disagreement as to the morphological 
nature of the sporangiophores of the Psilotacege. The two 
chief view^s are the following : ( i ) That the whole sporangio- 
phore is a single foliar member; (2) that it is a reduced axis 




Fig. 294. — Tmesipteris tannensis. A, Radial section of the young sporangiophore, 
X112; sy, the young synangium; B, similar section of an older sporangiophore, 
X112. The archesporial cells are shaded. C, Fully-developed synangium, show- 
ing its position between the two lobes of the sporophyll, X3; D, a longitudinal sec- 
tion of the synangium, showing the two loculi (all the figures after Bower). 



bearing a terminal synangium and two leaves. The recent very 
careful researches of Bower upon the origin of the sporangio- 
phore and synangium confirm the former view. He describes 
the development in Tmesipteris as follows : ''The apical cone 



XIII LYCOPODINEJE 509 

of the plant is very variable in bulk. ... In the large as well as 
the small specimens a single initial is usually present, but its seg- 
mentation does not appear to be strictly regular, and it is diffi- 
cult to refer the whole meristem to the activity of one parent 
cell. . . . When a leaf or sporangiophore is about to l>e formed, 
certain of the superficial cells increase in size, and undergo both 
periclinal and anticlinal divisions so as to form a m.assive out- 
growth, the summit of which is occupied, as seen in radial sec- 
tion, by a single larger cell of a wedge-like or prismatic form. . . . 
In these early stages I find it impossible to say whether the part 
in question will be a vegetative leaf or a sporangiophore, and 
even when older it is still a matter of uncertainty. . . . Those 
which are to develop as sporangiophores soon show an increase 
in thickness, while they grow less in length ; an excrescence of 
the adaxial surface soon becomes apparent (Fig. 294, A, sy), 
in which the superficial cells are chiefly involved. . . . The super- 
ficial cells at first form a rather regular series, which may be 
compared with the cells which give rise to the sporangia in Lyco- 
podium clavatwn, or in Isoefes: they undergo more or less regu- 
lar divisions, which, however, I have been unable to follow in 
detail : a band of tissue some four or more layers in depth is thus 
produced. About this period certain m.asses of cells assume 
the characters of a sporogenous tissue : but though they can be 
recognised as such by the character of the cells, it is extremely 
difficult to define the actual limits of these sporogenous masses." 

In Tmesipteris there are normally two masses of sporog- 
enous tissue corresponding to the two loculi in the mature synan- 
gium; in Psilotimi, which correspond closely with Tmesipteris 
in other respects, there are three. Whether additions are made 
to the sporogenous tissue from cells outside the original arch- 
esporium was not determined with certainty, but Professor 
Bower thinks it not improbable. In Psilotum the young arch- 
esporium is more clearly defined than in Tmesipteris, and it 
seems not unlikely that each sporogenous mass is referable to the 
division of a single primary archesporial cell. In both genera 
some of the sporogenous cells do not develop spores, but simply 
serve for the nourishment of the others, as in Equisetnm. 

The fully-developed synangium has the outer walls of the 
loculi composed of a single superficial layer of large cells, be- 
neath which are several layers of smaller ones (Fig. 294, D). 
The cells composing the septa are narrow tabular ones, with 



510 . MOSSES AND FERNS ' chap. 

firm woody walls marked by numerous pits. Occasionally the 
septum is partially absent and the loculi are thus thrown more 
or less completely into communication. The spores are usually 
of the bilateral form, like the microspores of Isoetes, but may- 
also be of the tetrahedral type. 

Bower regards the whole synangium as homologous with 
the single sporangium of Lycopodiurn, and also calls attention 
to its resemblance to the sporangium of Lepidodendron, with 
which the Psilotacese also show resemblances in the structure 
of the stem. 

The Affinities of the Psilotacece {Bower (21), Ford (i), 

Scott (i)) 

While the Psilotacese are usually united with the Lycopods, 
there has been of late a tendency to remove them from this class, 
and to aSsume a somewhat near affinity with the fossil Spheno- 
phyllales, whose relationships are usually considered to be with 
the Equisetales. The undoubted anatomical resemblances be- 
tween the Psilotacese and Lycopodiacese cannot be overlooked, 
and the question then remains whether these resemblances are 
anything more than analogies. 

The anatomy of the smaller shoots of the Psilotacese un- 
doubtedly recall the stem-structure of Sphenophyllum, and there 
seems to be also important points of resemblance in the sporan- 
gial structures. (Bower (21), Thomas (3)). 

Miss Ford ((i), p. 603), whose work on Psilotum is the 
most recent, considers the Psilotaceae to be much reduced forms, 
probably owing to their saprophytic habit. They are "some- 
what closely allied to the fossil group of the Sphenophy Hales." 



The Selaginellace^ 

Unlike the Filicineae, the heterosporous Lycopodinese out- 
number very much the homosporous forms, but all of the former 
may be reduced to a single genus, Selaginella, which contains 
nearly five hundred species, and, except for the presence of 
heterospory, approaches closely the genus Lycopodium, to which 
it is clearly not very distantly related. The great majority of 
the species of Selaginella belong to the tropics, and form a 



XIII 



LYCOPODINEJE 



5" 



characteristic feature of the forest vegetation of those regions. 
A few belong to the more temperate parts of Europe and Amer- 
ica, and a small number, e. g., S. riipestris, S. lepidophylla, 
grow in dry situations. 

The Gametophyte 

Hofmeister ( i ) included Selaginella among the other Pteri- 
dophytes he studied, but he was unable to make out the earlier 




Fig. 295. — A, B., C, Three views of the young' antheridium of Selaginella Kraussiana, 
X450; D, an older stage of the same, X480; E, F, two views of an older an- 
theridium of S. stolonifera, X480; G, spermatozoids of 6". cuspidata, X1170; x, 
vegetative prothallial cell; s, central cells (after Belajeff). 



stages of development of the prothallium. Later Millardet ( i ) 
and Pfeffer ( i ) made further investigations upon the same sub- 
ject, and added much to Hofmeister's account, but were also 
unable to determine the earliest phases of germination. 

Belajeff (i) has since given an accurate account of the 
germination of the microspores, and during the past ten years 
the development of the macrospores and female gametophyte 
has been very thoroughly investigated. 



512 MOSSES AND FERNS chap. 

The Microspores and Male Prothallium 

The microspores of all species of Selaginella are small and 
of the tetrahedral type. According to Belajeff (i) they may 
show either a distinct perinium, or the latter is not clearly sepa- 
rated from the exospore. The spores contain no chlorophyll, 
but include much oil as well as solid granular contents. At the 
time that the spores are shed each one has already divided into 
two very unequal cells, a very small lenticular cell (Fig. 295, x) 
and a much larger one which, as in Isoetes, becomes the single 
antheridium. 

The first wall in the antheridium divides it into two equal 
cells, each of which then divides into two others, a basal and 
an apical cell. The latter divides twice more, forming three 
segments, so that the young antheridium at this stage consists 
of eight cells arranged in two symmetrical groups. Of the 
three segments formed in each apical cell, the first and some- 
times the second form periclinal walls, so that a central cell 
(or two cells) is formed in each half of the antheridium, not 
unlike what obtains in Marsilia, and the young antheridium 
consists now of two (or four) central cells and eight peripheral 
ones. Belajeff states that the cell walls do not show the cellu- 
lose reaction, and that they are later absorbed. Where there are 
four primary central cells, these by further divisions produce 
a single cell-complex, which, after the disintegration of the per- 
ipheral cell walls, floats free in the cavity of the spore. Where 
but two primary central cells are formed, each produces a sepa- 
rate hemispherical cell mass. Belajeff does not state the num- 
ber of sperm cells formed. The spermatozoids (Fig. 295, G) 
are extremely small and closely resemble those of many Bryo- 
phytes, as well as Lycopodium. Like these they are always 
biciliate. 

Miss Lyon (2) has given a very different account of the 
male gametophyte in 5'. apus. She states that in this species the 
cytoplasm of the germinating spore contains large vacuoles sepa- 
rated by bands of cytoplasm, which radiate from the central 
"generative" nucleus. The latter, with its envelope of proto- 
plasm, then divides into "two cells," but how the membranes 
about these free cells are formed is not stated. These two cells 
give rise to the two masses of sperm-cells, and in the radiating 
vacuoles are formed granular masses which, to judge from the 



XIII LYCOPODINEJE 513 

figures, are astonishingly cell-like in appearance. Until it can 
be conclvisively shown that these are not really cells, the state- 
ment must be accepted with a certain amount of reservation. 

A recent examination by the writer of some of the germi- 
nating stages of the microspore of 5^. Kraiissiana has shown 
beyond question that in this species at least, Belajeff's statement 
as to the formation of a peripheral layer of cells about the sperm 
cells is correct. There was no trace of any vacuoles, the granu- 
lar cytoplasm filling the spore completely and the walls sepa- 
rating the peripheral cytoplasm from the central area were clear 
and unmistakable. No attempt was made to verify the exact 
succession of the division walls. 

The Macrospore and Female ProthalUum 

The formation of the female prothallium begins w^hile the 
spore is still within the sporangium, and long before it has 
reached its full size. 

At an early period, show^n first by Fitting (i), but later 
verified by Miss Lyon (2) and Campbell (25), the protoplast 
of the young macrospore separates from the inner spore mem- 
brane (Fig. 296, A), and the outer spore-membrane increases 
rapidly in size, so that a wide space separates the protoplasmic 
vesicle from the inner spore-membrane. The minute globular 
protoplast was mistaken by all the earlier observers for the pri- 
mary nucleus of the macrospore, as it is very evident through 
the transparent membrane at this time. The real nucleus is 
very small and divides very soon, but the cytoplasmic layer re- 
mains extremely thin. As the spore develops, the cytoplasmic 
vesicle rapidly increases in diameter and finally comes again into 
close contact with the endospore, or inner cellulose membrane 
(Fig. 296, B). There is a middle lamella or mesospore (m), 
which is very conspicuous in the early stages, as it is also, ex- 
cept at the apex of the spore, quite free from the thick outer coat, 
the exospore. The space between the mesospore and exospore 
is filled with a substance which stains faintly, and undoubtedly 
contains material which is used by the growing membranes. 

The nuclei (n) are small, and while the cytoplasmic layer 
remains thin, are flattened. Later they increase rapidly in num- 
ber, and with the thickening of the cytoplasmic layer, become 
globular in form. At first they are pretty uniformly distrib- 
uted, but later are more numerous at the apex of the spore; but 
33 



514 



MOSSES AND FERNS 



CHAP. 



at no time in ^. Kraussiana are they confined to this apical 
region, as Miss Lyon states is the case in S. apus. 

With the increase in the amount of protoplasm, the very 
large central vacuole becomes reduced in size, and finally, but 
this does not occur until after the germination of the spore, is 




Fig. 296. — A, Young macrospore of Selaginella helvetica. The vesicular protoplast, 
with the primary nucleus, is much smaller than the spore membranes, X400; B-E, 
S. Kraussiana, sections of the older macrospore, showing the development of the 
gametophyte; B, X about 200, the others more highly magnified; e, exospore; m, 
mesospore; n, nuclei; D, E, show the first cell- formation; D, vertical; E, horizontal 
section of spore-apex. (A, after Fitting). 



completely obliterated. In microtome sections it appears en- 
tirely empty, but Heinsen ( i ) states that in the living state it 
is occupied by great quantities of fatty oil. Whether this is 
the case in S. Kraussiana was not investigated. 



XIII 



LYCOPODINEJE 



515 



The protoplasmic layer is somewhat thicker at the apex, and 
here begins the first cell-formation (Fig. 296, D, E). There 
is but a single layer of nuclei at this point in S. Kraussiana. 
In 5'. apiis there may be, according to Miss Lyon, six or seven 
layers ; but none at all in the basal region of the spore. 

Cell-division begins in 6^. Kraussiana by the simultaneous 
appearance of delicate cell-walls between the nuclei at the apex 
of the spore. These walls cut out cells (areoles), each, at least 
in the central region, containing but a single nucleus. These 




Fig. 297. — Selaginella Kraussiana. A, Longitudinal section of a nearly ripe macro- 
spore, with the primary prothallium (Pr) complete, but still showing a large 
vacuole in the centre of the spore, X65; B, similar section of a younger stage, 
before the diaphragm has been differentiated, X400; n, free nuclei. 



areoles are at first open upon their inner side, and the first cell- 
formation resembles to a remarkable degree the typical endo- 
sperm formation in the Spermatophytes. Fig. 296, E shows a 
cross-section of the apex of the spore shortly after the first cell 
walls are complete. The extremely regular hexagonal form of 
the cells toward the centre of the prothallium is very noticeable. 
At the margin, and below, the cells are larger, and often contain 
several nuclei. 

The cell-formation does not extend at this stage to the base 
of the spore, as in Isoctes, but is confined to the apex, where a 
definite cellular body is formed. This is three-layered in the 
middle, but at the margins but one cell in thickness. The lower 
cells have the walls which are in contact with the spore-cavity 



5i6 MOSSES AND FERNS chap. 

much thickened at a later stage, and thus is formed the dia- 
phragm which is so conspicuous in most species, and which led 
Pfeffer to suppose that the first division in the young prothal- 
lium proper from the lower part of the spore, in which later the 
"secondary endosperm" is formed. 

Scattered through the protoplasm of the spore-cavity below 
the diaphragm are numerous nuclei. The protoplasmic layer 
becomes rapidly thicker (Fig. 297, A), and finally completely 
fills the cavity of the spore. The thickenings upon the outer 
spore-coat are very evident even before the primary nucleus 
divides, and they increase rapidly in size, as the spore develops. 
A very casual examination suffices to show that the tapetal cells 
of the sporangium here play a most important part, not only 
in the development of the spore-coat, but also in the growth 
of the prothallium. The rapid increase in the amount of pro- 
toplasm in the spore during the growth of the prothallium, as 
well as the growth of the spore itself, can only be accounted for 
by the activity of these cells, which are in close contact with 
the spore, and show every evidence of being active cells, through 
whose agency the materials are conveyed to the spore for its 
further development. 

The first archegonia begin to form shortly before the spores 
are shed, and soon after, the exospore splits along the three ven- 
tral ridges and exposes the central part of the prothallium. 
This, like that of Isoetes, is quite destitute of chlorophyll, and 
is entirely dependent upon the food materials in the spore for 
its further development. About this time also begins the cell- 
formation in the part of the spore below the diaphragm (Fig. 
298). This is simply a continuation of the same process by 
which the apical tissue was developed, but the cells are larger 
and more irregular! 

The archegonia are produced in considerable numbers, and 
apparently in no definite order. Their development corre- 
sponds with that of Lycopodium, but the neck is very short, 
like that of the Marsiliacese, each row of neck cells having but 
two cells. No basal cell is formed, and the central cell is sepa-* 
rated from the diaphragm only by a single layer of cells. The 
neck canal cell (Fig. 298) is broad, like that of Isoetes, but the 
nucleus does not, apparently, divide again. The egg (Fig. 298, 
E) shows a distinct receptive spot, and the nucleus is clearly de- 
fined. At this stage the diaphragm is very evident and much 



XIII 



lYCOPODlNE^ 



517 



thickened, so that the archegonial tissue of the prothalhum is 
very sharply separated from the nutritive tissue below. 

Sometime after germination begins, the vacuole completely 
disappears, and sometimes a spongy-looking mass was seen 
filling it before it finally disappeared. In the later stages, the 
nuclei in the cytoplasm immediately below the diaphragm are 
much more numerous and correspondingly smaller than those 
in the much more coarsely granular cytoplasm of the basal 
region. The finely granular protoplasm and numerous nuclei 





Fig. 298. — Selaginella Kraussiana. A, Nearly median section of a fully-developed 
female prothallium, showing the diaphragm (d) , X180. One of the archegonia 
has been fertilised, and the suspensor (sus) has penetrated through the diaphragm 
into the tissue below it; B-E, development of the archegonium, X360; F, two- 
celled embryo, belonging to the suspensor shown in A, X360; G, end of a sus- 
pensor with two-celled embryo {em), X360. 



show the region where the cell-formation begins which results 
in the secondary prothallial tissue. 

Arnoldi ( i ) states that in ^. ciispidata there is a single 
large primary nucleus near the apex of the spore which is com- 
pletely filled with cytoplasm. It looks very much, however, 
as if he had mistaken the protoplasmic vesicle of the young 



5i8 



MOSSES AND FERNS 



CHAP. 



Spore for the nucleus — if his statement is correct, S. cuspidata 
differs very remarkably from other investigated species in the 
development of the gametophyte. 

Miss Lyon (2) found in both vS'. apus and US', rupestris a 
much greater development of the primary prothallial tissue than 
is found in 5'. Kraussiana. To judge from her figures 54 and 
55, there are two types of prothallium in S. apus, one in which 
the base of the primary prothallium is sharply delimited, and 
the other without any clear boundary between the primary and 
secondary prothallial tissues. 

The Embryo 

The first division in the fertilised ovum is transverse, and 
as in Lycopodium, the cell next the archegonium neck becomes 




G ^ F 

Fig. 299. — Selagmella Martensii. Development of the embryo (after Pfeffer). A, B, 
D, E, Successive stages in longitudinal section, X340; C, apical view of a young 
embryo with four-sided apical cell {x), X340; F, longitudinal section of the primary 
root, X205; G, apex of the young sporophyte, showing the first dichotomy, X340i 



the suspenso'r. This in Selaginella is much more developed, 
however, and grows at first more actively than the lower cell 
from which the embryo proper arises. The upper part of the 



XIII LYCOPODINE^ 519 

suspensor enlarges somewhat, and forms a bulbous body, which 
completely fills the venter of the archegonium. The suspensor 
grows rapidly downward, penetrating the diaphragm and push- 
ing the young embryo down into the mass of food cells which 
occupy the space below it. The suspensor is very irregular 
in form, and undergoes several divisions (Fig. 298, G). 

The first division in the embryo proper is almost vertical 
(Fig. 298, F), and divides it into nearly equal parts. Beyond 
this the early stages ot che embryo w^ere not followed by the 
writer, but to judge from the later stages, they correspond to 
those of S. Marteusii, which has been most carefully studied 
by Pfeffer ( i ) , the substance of whose work may be given as 
follows. After the first w^all is formed in the embryo, there 
arises in one of the cells a second, somewhat curved one, which 
strikes the primary wall about half-way up. The cell thus cut 
of¥, seen in longitudinal section, is triangular, and is the apical 
cell of the stem (Fig. 299, A). The two other cells (leaf- 
segments) now undergo division by a vertical wall, which 
divides each into equal parts, and each of these pairs of cells 
develops into a cotyledon. The apex of the young cotyledon 
is occupied by a row of marginal cells in w'hich divisions are 
formed, like those in the apical cell of the stem, and in longi- 
tudinal section the apex of the cotyledon seems to have a single 
apical cell, much like the stem (Fig. 299, E). From the larger 
of the leaf-segments, by a more active growth of the cells next 
the suspensor, the foot is formed, and by its growth the stem 
apex is pushed to one side, and its axis becomes almost at right 
angles to that of the suspensor. Each cotyledon develops upon 
its inner side, near the base, an appendage, the ligula (Fig. 
300, /), which is a constant character of all the later leaves. 

The primary root, as in Lycopodium, forms late, and no 
trace of it can be seen until the other parts are evident. It 
arises in the larger leaf-segment, close to the suspensor, and 
therefore is separated from the cotyledon by the foot. The 
root-cap arises from a superficial cell, w^hich divides early by 
both periclinal and anticlinal walls, and thus becomes two lay- 
ered. From a cell immediately below is derived the single 
apical cell to wdiich the subsequent growth of the root is due. 
The further divisions in the primary root were not followed. 

The axes of the stem and root soon develop a strand of 
procambium which is continuous in the two, but to judge from 



520 



MOSSES AND FERNS 



CHAP. 



Pfeffer's figures, the cotyledons do not develop their vascular 
bundles until later. The early growth in length of the root 
is mainly intercalary, as the divisions in the apical cell for some 
time are not very rapid, and for a long time the root-cap con- 
sists only of the two original layers. 

With the growth of the embryo the cell-formation in the 
lower part of the spore continues until it is filled with a contin- 
uous large-celled tissue, the contents of whose cells are much 
less granular than the undivided regions of the spore, and as 
the embryo develops, the foot crowds more and more upon them 

until it nearly fills the 
spore cavity. 

On comparing Pfeffer's 
account of wS^. Martensii 
with my own observations 
upon vS. Kraussiana, the 
main differences consist 
first in the smaller devel- 
opment in the latter of 
the primary prothallium, 
i. e., the prothallial tissue 
formed before the spores 
are shed, the archegonia 
being only separated from 
the diaphragm by a single 
layer of cells instead of by 
three or four, as in S. 
Martensii. L. apus, which 
was also examined by the 
writer, is intermediate in 
this respect between the 
two. A second difference 
is the later period at which the cell division in the lower part of 
the prothallium is completed in 5^. Kraussiana. In this species, 
too, no rhizoids were seen, while Pfeffer observed them in 6'. 
Martensii. Finally, in the latter the suspensor is much shorter 
and straighter than in 6^. Kraussiana. Miss Lyon (2) found 
that in S. apus no suspensor was formed, but the development 
of the embryo is not described. 

In ^S. Martensii, almost as soon as the cotyledons are estab- 
lished, the two-sided apical cell of the stem is replaced by a' 




Fig. 300. — Longitudinal section of a fully- 
developed prothallium of S. Kraussiana, 
with an advanced embryo {em), X77', I, 
lignala. 



XIII 



LYCOPODINE^ 



521 



four-sided one, from which are then produced two similar ones 
by the formation of a median wall, and a true dichotomy of the 
primary axis thus takes place at once, the two new branches 
growing out at right angles to the cotyledon. While this may 
also occur in .9. Kraussioua (Fig. 301, D), it is not always the 
case, and frequently the young plant remains unbranched until 
it has reached a length of a centimetre or more, and has pro- 
duced numerous leaves. 




Fig. 301. — Selaginella Kraussiana. A, Macrospore with the prothallium {pr), X50J ^» 
young sporophyte still attached to the spore {sp), X8; cot, cotyledons; R, root; C, 
upper part of an older stage, X6; D, a still older one showing the first di- 
chotomy, X4. 



The embryo of S. spinulosa (Bruchmann (4) ) has a short 
and massive suspensor, and no foot is developed. 

Miss Lyon (2) found that in both S. apus and S. rupestris, 
fertilisation occurred w^hile the spores were still within the spo- 
rangium, and the sporangium attached to the strobilus. ''The 
strobilus of ^. rupestris retains its physiological connection 



522 MOSSES AND FERNS chap. 

with the plant until the embryo has produced the cotyledons 
and root." (/. c, p. 183). 

In kS'. apus, the strobili are shed in the early autumn, whether 
fertilisation has occurred or not. ^. rupestris retains the stro- 
bili through the winter, and fertilisation is effected in the spring. 

From some partial observations made by the writer upon 
spores of a species (probably L. Bigelovii) from the dry 
region of southern California, it looks very much as if, in this 
species, the spores became completely dried up after the embryo 
had already attained some size, and that the spores remained 
in this condition through the dry season, the embryo resuming 
its growth again in the autumn. 

The Adult Sporophyte 

The genus Selaginella is a very large one, but there is some 
difference of opinion as to the number of species. Hierony- 
mus (i) enumerates 559 species, while Underwood (4) says 
the genus contains "about 335" species. The genus is usually 
divided into two subgenera, Euselaginella {Homoeophyllunv 
of Hieronymus) and Stachygynandnim {Heterophyllum, 
Hieronymus). In the first are included those species in which 
the leaves are all alike and arranged radially about the shoot, 
which is generally more or less completely upright. vS'. rupes- 
tris, S. selaginoides and 5^. Bigelovii are examples. In Stachy- 
gynandnim, which comprises the majority of the species, the 
shoot is dorsi ventral, and often prostrate. The leaves are 
four-ranked, those of the two dorsal rows being much smaller 
than the others (Fig. 302). The first type suggests the species 
of Lycopodinm of the type of L. annotinum, the second that of 
L. complanatnm or L. vohihile. In many species there is a 
creeping stem from which upright branches grow, much as in 
many species of Lycopodium, but in others there is no clear dis- 
tinction between these parts. The roots may arise directly 
from the ordinary branches, but in many species, e. g., S. 
Kraussiana, they are borne at the end of peculiar leafless 
branches or rhizophores (Fig. 305, A). These, like the stem, 
show an apparently regular dichotomous branching, which, 
however, is really monopodial. The leaves, like those of Lyco- 
podium, are small, more or less lanceolate in outline, and with a 
single median vein. In the homophyllous forms the sporo- 



XIII 



LYCOPODINEAi 



523 



phylls differ but little in appearance from the ordinary leaves, 
but in the heterophyllous ones they are smaller tlian the other 
leaves, and form a strobilus much like that of Lycopodium, but 
usually less conspicuous. 

The strobilus (Hieronymus (i), p. 653) may be either 
erect or horizontal; much more rarely it is pendent, and there 
appears to be a certain relation between the arrang-ement of the 
sporophylls and the position of the strobilus. Where it is up- 
right the sporophylls are all alike, and dis])osed radially about 
the axis. Where the strobilus is horizontal it is more or less 
markedly dorsiventral in structure. In 5^. selaginoides and 5". 
deflexa there is a more or less perfect spiral arrangement of the 




Fig. 302. — A, Part of a fruiting plant of Selaginella Kraussiana, X3; sp, sporangial 
strobilus; R, young rhizophore; B, longitudinal section of the strobilus, X5; >"a, 
macrosporangium ; mi, microsporangium. 



Sporophylls, but in all the other species they are four-ranked. 
Usually in the latter case the sporophylls are alike, but there 
may be the same difference in the dorsal and ventral leaves of 
the dorsi-ventral strobili that is found in the sterile shoots of the 
same species. 

The basal leaves of the strobilus may be sterile, but usually 
each sporophyll subtends a sporangium. In ^. Kraussiana, 
and many other species of the same section of the genus, there 
is but a single macrosporangium developed — the first formed 



524 



MOSSES AND FERNS 



CHAP. 



Sporangium of the strobilus. This is much larger than the 
microsporangia, and the sporophyll correspondingly large. 
In other species, e. g., S. apus, there may be several macrospo- 
rangia. According to Hieronymus the position of the stro- 
bilus conditions to some extent the development of macrospo- 
rangia, which are either basal, or in that part of the strobilus 




Fig. 303. — Selaginella Kraussiana. Horizontal section of the apex of the stem, X77; B, 
the apical meristem of the same, X4S0; s, the apex of the main axis; s', a young 
lateral branch; B, B, young leaves; L, ligula of the leaf; C, D, longitudinal sec- 
tions of the base of older leaves, X450; i, i, lacuna surrounding the vascular bun- 
dles of the stem; t, one of the trabeculae. 



nearest the ground. Thus in dorsiventral strobili they are de- 
veloped on the ventral side ; in pendent ones they may form at 
the apex of the strobilus. Miss Lyon made some interesting 
observations upon the development of the sporangia in vS'. apus 
and 5'. rupestris. In the latter species the strobili begin to de- 



XIII 



LYCOPODINE^ 



525 



velop in the late summer and autumn, producing at this time 
only macrosporangia. In the spring the growth of the stro- 
bilus is resumed, and microsporangia are developed, the game- 
tophytes produced from the macrospores of the previous year 
being fertilised by spermatozoids developed from the micro- 
spores developed in the spring. In 6^. apus there was evidence 
that the embryos formed in the autumn passed through the 
winter within the macrospore, completing their development in 
the spring. 

The leaves arise much in the same w^ay that the branches 
do, but do not develop a single apical cell. The growth is 




Fig. 304.— -Cross-section of a fully-developed stem of 5". Kraussiana, showing the two 
vascular bundles suspended in the large central lacuna by means of the trabeculae 
U), X75; B, a single vascular bundle, X450; x, x, scalariform tracheids; s, s, 
sieve-tubes. 



much the same as in the first leaves of the embryo, and as in 
these the early growth is due mainly to a row of marginal 
initial cells from which segments are cut off alternately above 
and below. 



526  MOSSES AND FERNS chap 

If we examine a longitudinal section of the stem a short 
distance below the apex (Fig. 303, A), we find a regular inter- 
cellular space formed between the central stele (or steles), 
which completely surrounds it, and becomes very conspic- 
uous as the section is examined lower down. The formation 
of this lacuna is similar to that in the capsule of the Bryales, 
and, as there, the central mass of tissue is connected by 
rows of cells with the outer tissue. These rows of cells (tra- 
beculse) are at first composed of but a single cell, but later by 
tangential walls become slender filaments by which the vascu- 
lar cylinders are suspended in the large lacuna which occupies 
the centre of the stem (Fig. 304, t). According to Stras- 
burger ( (7), p. 457) both the trabeculse, which are usually re- 
garded as endodermal, and the pericycle, are of cortical origin. 

The fully-developed bundle in S. Kraussiana (Fig. 304, B) 
shows a pericycle composed of a single layer of rather large 
cells, within which lies the phloem, which completely surrounds 
the xylem, as in the Ferns. The sieve-tubes in this species 
form a single circle just inside the pericycle, but according to 
Gibson ( (2), p. 176) are absent opposite the protoxylem. He 
states that there is but a single group of protoxylem elements 
here, but my own observations lead me to think that there are 
two, as Russow affirms is the case. The origin of the proto- 
xylem was not traced, but the appearance of the mature bundle 
in the specimens examined (Fig. 304, B) points to this con- 
clusion. The protoxylem is made up of small spiral and an- 
nular tracheids, the metaxylem (secondary wood) of larger 
scalariform elements, as in Lyco podium. The sieve-tubes 
have delicate walls and numerous, but poorly developed, sieve- 
plates upon their lateral walls. 

While in the main the anatomical characters are essentially 
the same in all species examined, there are a number of differ- 
ences to be noted (Gibson (i, 2)). Thus the stem may be 
monostelic (S. Martensii), bistelic (S. Kraussiana), polystelic 
(S. Icevigata). In the former species the presence of silica in 
the inner cortex has been demonstrated by Strasburger, and 
Gibson has shown the same thing in other species. In this 
species, too, besides the simple trabeculae found in S. Kraus- 
siana, others occur in which the outer cells undergo divisions in 
more than one plane, and form a group of cells with which the 
endodermal cell is articulated. In all species examined these 



XIII 



LYCOPODINEAl 



S27 



cells show more or less marked cutinisation. The number of 
protoxylems in most species is two, but there may be accessory 
ones. 

The cortex is composed in most species of delicate paren- 
chyma, with few or no intercellular spaces, and most of the 
cells contain chlorophyll. In species like S. lepidophylla, which 
grow in dry localities, the cortical cells are sclerenchymatous, 
with deeply-pitted walls and no lacunae are present in the stem. 
In the creeping stems, even in polystelic species, there is but a 
single stele, which gradually passes over into the separate steles 
of the upright stems. 




Fig. 305. — A, Rhizophore, with roots of 5". Kraussiana, Xi^A; B, cross-section of the 
vascular bundle of a root, X430; C, median longitudinal section of the leaf, X215. 



The Leaf (Gibson {4, 5); Hieronymiis (i)) 

• 

The leaves of Selagmella are always of simple structure, 
much like those of Lyco podium. Gibson (4, 5) has made an 
exhaustive study of their structure, and the following account 
is based upon his studies. 

The leaf may be perfectly symmetrical in outline, or may 
have one side more developed than the other. In some species 
there are characteristic basal appendages, or auricles. 

A section of the leaf (see also Fig. 303) In most species 
shows a definite upper and lower epidermis, which may be com- 



528 MOSSES AND FERNS ' chap. 

posed of similar cells, e. g., S. rupestris, or of cells of somewhat 
different form on the two surfaces of the leaf, e. g., S. Mar- 
tensii. Some of the epidermal cells may have the form of 
sclerenchymatous fibres (S. stiberosa). The mesophyll is com- 
posed of a loose network of cells, which may be all alike (vS'. 
rupestris) or less frequently, there is developed below the upper 
epidermis, a palisade parenchyma (S. Lyallii). As a rule 
stomata are formed only upon the lower epidermis, but there 
are some exceptions. 

The single median vascular bundle is concentric in struc- 
ture, and the leaf-traces join the vascular cylinder of the stem, 
as they do in Lycopodium. The xylem consists of a single row 
of annular tracheids, and three or four spiral ones. The 
phloem is mainly composed of elongated parenchyma cells, but 
one or two sieve-tubes can usually be demonstrated. Sur- 
rounding the bundle is a pericycle consisting of a single layer 
of cells, or in some cases more, but no definite endodermis is 
present. 

There is ahvays developed at the base of the leaf the char- 
acteristic ligula (Fig. 303, /). This develops at an early 
period, and seems to be an organ for retaining moisture, as its 
young cells develop abundant mucilage. In its fully developed 
condition it shows a basal portion (glossopodium) composed 
of large cells which are surrounded by a sort of sheath which is 
continuous with the epidermis of the leaf. It varies in form in 
different species. Thus in S. Vogelii it is tongue-shaped; in 
S. Martensii, fan-shaped; in wS". cuspidata, fringed (for further 
details of its structure and development see Gibson (4)). 

Simple hairs are of frequent occurrence in various parts of 
the sporophyte. 

The Chloroplasts 

The chloroplasts of Selaginella are peculiar, on account of 
their large size and small numbers. A careful study has been 
made of these by Haberlandt (9), wh6 found that in each of 
the meristematic cells of the stem apex a single plastid was 
present. This in the assimilative cells of the leaves either re- 
mains undivided (S. Martensii) , or it may become more or less 
completely divided into two (S. Kraussiana) . In vS. Willde- 
nowii there may be as many as eight. In the cortical paren- 



XIII 



LYCOPODINEJE 



529 



chyma of the stem the chloroplasts are apparently of the ordi- 
nary form, but a careful examination shovv^s that they are all 
connected, and are directly referable to the divisions of the 
primary plastid in the young cell. In all cases the nucleus is in 
contact with the chloroplast or group of chloroplasts (Fig. 
306). The character of the chloroplasts here has its nearest 
analogy in Anthoceros, where occasionally a division of the 
chloroplasts is met with, especially in the elongated cells of the 
sporogonium. 




n..-"i»'j 



Fig. 306. — A, B, Cells of the mesophyll of Selaginella Martensii showing" the single 
chloroplast (c/) and the nucleus (n) ; C, chain of connected oval chloroplasts from 
the inner cortex of the stem of S. Kraussiana, X640 (after Haberlandt). 



The Roots 



The roots in S. Kraussiana are borne upon the special leaf- 
less branches or rhizophores, w^hich in structure are much like 
the stem. Previous to the formation of the first roots upon the 
rhizophore (Sadebeck (6) ), the apical cell is obliterated and re- 
placed by a group of initial cells. The apical cells of the (usu- 



AA 



530 



MOSSES AND FERNS 



CHAP. 



ally two) roots formed arise secondarily, and quite independ- 
ently of each other, from cells lying below the surface, and 
covered with one or two layers of cells. These cells soon as- 
sume a tetrahedral form, and become the apical cells of the pri- 
mary roots. The branching of the roots, Hke that of the stem, 
is really monoppdial, although apparently a true dichotomy. 
The vascular bundle of the root is monarch (Fig. 305, B), 
and does not show a distinct endodermis. The phloem sur- 
rounds the xylem completely, but apparently sieve-tubes are 




J.-L 




D. 





Fig. 307. — Selaginella Kraussiana. Development of the microsporangium, radial sec- 
tions. A-C, X500; D, X235. The nuclei of the archesporial cells are shown. 
L, The leaf subtending the sporangium. 

not developed opposite the protoxylem. The elements of the 
bundle are in structure like those of the stem-bundles. 

The Sporangium (Goebel (16) ; Bower (13)) 

The development of the sporangium is much like that of Ly- 
copodmm, and has been studied by Goebel and Bower in 5. 
spinosa, and by the latter in .S'. Martensii also. In S. Kraus- 
siana (Fig. 307, A) a radial section of the young sporangium 
shows a very regular arrangement of the cells, with a single 
central archesporial cell (the nucleated cell of the figure). 
This evidently has arisen from a hypodermal cell of the central 
row, and from it is already cut off by a periclinal, an outer cell. 



XIII 



LYCOrODINEJE 



531 



The whole closely resembles Goebel's figures of 6^. spinosa. A 
comparison with older stages indicates that from this central 
cell alone the sporogenous cells are produced, as in Lycopodium 
selago. The outer row of cells does not divide by periclinal 
walls, and from the first forms an extremely distinct layer. 
The first cell cut off from the archesporium divides again by a 
periclinal wall (Fig. 307, B), and the inner cell forms prob- 
ably the first tapetal cell, although in some cases it looks as if 
this cell took part in the formation of spores. The arche- 






FiG. 308. — Selaginella Kraussiana. A, Radial section of a nearly ripe microsporangium, 
Xioo; /, ligula of the subtending leaf; t, itapetum; B, section of young macro- 
sporangium (about half grown), showing the papillate tapetal cells it), X6oo; C, 
section of the wall of a young macrospore from the same sporangium, X6oo. 



sporium undergoes repeated divisions to form the sporogenous 
tissue, and finally the layer of cells between this and the pri- 
mary wall divides by periclinal w^alls to form the tapetum, 
which here remains intact until the spores are nearly or quite 
mature. The formation of the stalk is the same as in Lyco- 
podium. 

It is quite possible that the apparently single archesporial 
cell of wS'. Kraussiana may be one of a transverse row of arche- 
sporial cells, like those of 5'. Martensii. 



532 MOSSES AND FERNS chap. 

Miss Lyon (2) thinks that in both S. apiis and 5^. rupestris 
the whole sporangium may be traced back to a single super- 
ficial cell, which she calls the archesporium. 

Bower (15) considers it probable that in S. spinosa and 6". 
Martensii the sporogenous tissue cannot be traced back always 
to a single cell (in radial section), and has also shown that 
when tangential sections are examined, as in Lyco podium, the 
archesporium always is a row of cells. 

In all species of Selaginella yet examined, the sporangium 
is not of foliar origin, but originates from the axis above the 
insertion of the leaf by which it is subtended. 

As in Lycopodiuni the tapetal cells do not become disorgan- 
ised, but remain intact as the inner layer of cells of the three- 
layered sporangium wall. They form an epithelium-like layer 
of papillate cells, distinguished by their dense granular con- 
tents, and it is evident that they are actively concerned in the 
elaboration of nutriment for the growth of the young spores 
(Fig. 308). 

As in the other heterosporous Pteridophytes, the two sorts 
of sporangia are -alike in their earlier stages, and this in Sela- 
ginella continues up to the time of the final division of the spore 
mother cells. In the microsporangium, all of the sporogenous 
cells undergo the usual tetrad division; but in the macrospo- 
rangium only a single one normally divides. Occasionally 
one -of the divisions is suppressed so that but two macrospores 
result. In the microsporangium all of the spores mature, and 
the spores remain small. The single tetrad of macrospores in- 
creases enormously in bulk, and finally completely fills the mac- 
rosporangium, which is itself much larger than the microspo- 
rangia, and by the crowding of the enclosed spore-tetrad, as- 
sumes a four-lobed form. The cells of the wall remain green 
and fresh up to the time that the macrospores are ripe, and 
sections show that the tapetal cells are in close contact with the 
wall of the spores. The episporic ridges are very evident be- 
fore the spore has reached half its final diameter, and sections 
of the spore wall at this time (Fig. 308, C) show the spine-like 
section of the surface ridges. The wall rapidly increases in 
thickness as the spores grow, and this increase is evidently due 
almost entirely to the activity of the tapetal cells, as the spore 
at this stage contains very little protoplasm. The first nuclear 
division in the macrospore takes place when the spore is about 



XIII LYCOPODINE^ 533 

half-grown, and by the time it has reached its full size the cell 
divisions in the apical region are complete and the archegonia 
have begun to form. (For details of the spore-development 
in Selaginella see Fitting ( i ) ) . 

The ripe sporangium opens by a vertical cleft, as in Lyco- 
poditim. Goebel (22) has recently descril^ed in detail the 
mechanism involved in the dehiscence of the sporangium. 

The Affinities of the Lycopodinece 

Among the living Lycopodinese there are two well-marked 
series, one including the Lycopodiacese and Selaginellacese, the 
other the Psilotaceae. In the first, beginning with Phylloglos- 
sum, the series is continued through the different forms of 
Lycopodium to the Selaginellacese. The relation of the Psilo- 
taceae to this series is doubtful, and must remain so until the 
sexual generation of the former is known. The probable 
saprophytic or parasitic life of these plants makes it impossible 
to determine just how far their simple structure is a primitive 
character rather than a case of degradation. 

Of the first series, it seems probable that of the forms whose 
life history is known, the type of L. cernimm represents the 
most primitive form of the gametophyte. It is reasonable to 
suppose that in all these forms the prothallium w^as green, and 
that the saprophytic prothallia, like those of L. phlegmaria and 
L. annotinum, are of secondary origin. The prothallium, of 
the type of L. cerminm, may be directly connected W'ith the 
Bryophytes and resembles them also in the small biciliate 
spermatozoids, in which latter respect all the Lycopodineae yet 
examined agree. This latter point is perhaps the strongest 
reason for assuming that the Lycopods represent a distinct line 
of development, derived directly from the Bryophytes, and not 
immediately related to either of the other series of Pterido- 
phytes. The character of the archegonium, as well as the long 
dependence of the embryo upon the prothallium and the late 
appearance of the primary root, point to the genus Lycopodium 
as a very primitive type, even more closely related to the Bryo- 
phytes than are the eusporangiate Ferns. Phylloglossmn, at 
least so far as the sporophyte is concerned, is the simplest liv- 
ing Pteridophyte. 

The close relation of Selaginella to Lycopodimn is suf- 



534 MOSSES AND FERNS chap. 

ficiently obvious. It is, however, interesting to note that Sel- 
aginella seems to have retained certain characters that are ap- 
parently primitive. These are the presence of a definite apical 
cell in the stem and root of most species, and the peculiar chlo- 
roplasts, which are especially interesting as a possible survival 
of the type found in so many Confervaceae, e. g., Coleochcete, 
from which it is quite likely that the whole archegoniate series 
has descended. This form of chloroplast occurs elsewhere 
among the Archegoniatse only in the Anthocerotes. 

In the characters of the sporangium and the early develop- 
ment of the prothallium, Selaginella undoubtedly shows the 
closest affinity to the Spermatophytes, especially the Gymno- 
sperms, of any Pteridophyte. The strobiloid arrangement of 
the sporophylls and the position of the sporangia are directly 
comparable to the strobilus of the Coniferse. The wall of the 
sporangium is here not only morphologically, but physiologic- 
ally comparable to the nucellus of the ovule, and the macro- 
spore grows, not at the expense of the disorganised spo- 
rogenous cells and tapetum alone, but is nourished directly 
from the sporophyte through the agency of the cells of the 
sporangium stalk and wall, until the development of the en- 
closed prothallium is far advanced. The latter, both in its 
development while still within the sporangium, as well as in 
all the details of its formation, shows a close resemblance to 
the corresponding stages in certain Conifers. The formation 
of a "primary" and "secondary" prothallium is, as we have 
seen, only apparent, and the diaphragm in the prothallium of 
Selaginella is not a true cell wall, marking a primary division 
of the spore contents, but only a secondary thickening of the 
lower walls of certain cells, indicating a temporary cessation in 
the process of cell-formation. It is by no means improbable 
that this cell-formation may sometimes go on uninterruptedly, 
in which case no diaphragm would be formed, and, as in Isoetes, 
there would be no distinct line of demarcation between the 
archegonial tissue at the apex and the large-celled nutritive 
tissue below. 

The presence of a suspensor in all investigated Lycopodinese 
is a character which distinguishes them at once from the other 
Pteridophytes, and has its closest analogy again among the 
Conifers. 

The possibility that the Psilotacese may not be directly re- 



XIII LYCOPODINE^ 535 

lated to the other Lycopodinec-E has been referred to. As noth- 
ing is known at present of the gametophyte and embryo, this 
point must, for the present, remain open. 

Fossil LycopodinecB 

Many fossil remains of plants undoubtedly belonging to the 
Lycopodinese are met with, especially in the Coal-measures, 
where the Lepidodendreae were especially well developed. Of 
homosporous forms, it seems pretty certain that the fossils 
described under the name Lycopodites are related to the living 
genus Lycopodiiim, and certain fossils from the Coal-measures 
have even been referred to the latter genus, some of these being 
homophyllous, others heterophyllous. Solms-Laubach thinks 
it somewhat doubtful whether the plants described by various 
writers, and belonging to older formations, really are Lyco- 
podineae. 

In regard to the Psilotacese he says : ''The statements re- 
specting fossil remains of the family Psilotacece are few and un- 
certain, nor is this surprising in such simple and slightly differ- 
entiated forms. If Psilotites . . . does really belong to this 
group, a point which I am unable to determine from the figures, 
we should be able to follow the type as far down as the period 
of the Coal-measures." 

A discussion of some of the numerous characteristic fossil 
Lycopods will be left for a special chapter. 



CHAPTER XIV 

ISOETACE^ 

The genus hoetes, the sole representative of the family Isoe- 
tacese, differs so much from the other Pteridophytes that there 
has been a good deal of difference of opinion as to where it 
should be placed, hoetes is most commonly associated with 
Selaginella, and there are undoubtedly marked resemblances be- 
tween the two genera in certain anatomical details, and in the 
development of the spores and gametophyte. On the other 
hand, the embryo and the spermatozoids are much more like 
those of the lower Ferns, with which they have sometimes been 
associated. Whether the Isoetacese are assigned to the Fili- 
cinese or Lycopodinese, they are sufficiently distinct to warrant 
the establishment of a separate order, Isoetales. 

According to Sadebeck (8), there are 62 species of hoetes. 
Of these sixteen are found in the United States. 

hoetes has been the subject of repeated investigation, Hof- 
meister (i) being the first to study its development in detail. 
The sporophyte is in most species either aquatic or amphibious, 
but a few species are terrestrial. They are very much alike in 
appearance, having a very short stem whose upper part is com- 
pletely covered with the overlapping broad bases of the leaves, 
which themselves are long and rush-like, so that the plant in 
general appearance might be readily taken for an aquatic 
Monocotyledon. The roots are numerous and dichotomously 
branched. The stem grows slowly in diameter, and the older 
ones show two or three vertical furrows that unite below, and 
as the stem continues to grow these furrows deepen, so that the 
old stem is strongly two or three lobed. In the furrows the 
roots are formed in acropetal succession. The leaves are closely 

set and expanded at the base (Fig. 309) into a broad sheath, 

536 



XIV 



I SORT ACE JE 



537 



with membranaceous edges. Just above the base of each per- 
fectly-developed leaf is a single very large sporangium, sunk 
more or less completely in a cavity (fovea), which in most 




Fig. 309. — A, Plant of Isoetes Bolanderi, X 1 ; B, base of a leaf with macrosporan- 

gium, X4; /, ligula; v, velum. 



Species is covered wholly or in part by a membranaceous indusi- 
iim (velum), and above the fovea is a scale-like outgrowth of 



538 



MOSSES AND FERNS 



CHAP^ 



the leaf, the ligula. The spores are of two kinds, borne in sepa- 
rate sporangia. The outer leaves of each cycle produce micro- 
spores, the inner ones macrospores, many times larger than the 
former. The innermost leaves, which are not usually perfectly 
developed, are sterile, and separate one year's growth from the 
next. In some of the land forms, e. g., I. hystrix, these sterile 
leaves are very much reduced, and form spine-like structures. 

The Gametophyte 

The germination of the microspores was studied by Hof- 
meister (i), and later by Millardet (i) and Belajeff (i), the 




Fig. 310. — A-G, Isoetes echinospora, var. Braunii. Development of the antheridium, 
X about 1000. H, Spermatozoid of /. Malinverniana (H, after Belajeff). 



later writer differing in some essential particulars from the 
earlier observers. The two former studied /. lacustris, the lat- 
ter, /. setacea and I. Malinverniana, which do not seem to differ, 
however, from /. echinospora, which was investigated by 
the writer. The microspores of all the species are bilateral, and 
are small bean-shaped cells with thick but in most species nearly 
colourless walls. The epispore sometimes has spines upon it^ 



XIV ISO ET AC EM 539 

but in /. echinospora var. Braiinii the surface of the spore is 
nearly smooth. In this species the spores begin to ripen in the 
early autumn, and continue to do so as long as the conditions 
permit of growth. The spores are set free by the decay of the 
sporangium wall, which probably in nature is not completely 
the case until winter or early spring, which seems to be the 
natural time for germination. If they are set free artificially, 
however, they will germinate promptly, especially if this is done 
late in the autumn or during the winter. Thus spores sown in 
December produced free spermatozoids in two weeks. The 
spores do not all germinate with equal promptness, and all 
stages of development may be met with in the same lot. The 
ripe spore has no chlorophyll, but contains besides the nucleus, 
albuminous granules, small starch grains, and oil. 

The first division wall cuts off a small cell from one end, 
which undergoes no further development, and represents the 
vegetative part of the prothallium, which is here absolutely 
rudimentary. The rest of the spore forms at once the single 
antheridium. In the latter two, walls are formed so inclined to 
each other as to include two upper cells and one lower one ( Fig. 
310, C). This latter next divides into two by a vertical longi- 
tudinal wall, and each of the resulting cells is further divided 
by a periclinal wall, so that the antheridium consists of four per- 
ipheral cells and two central ones. The latter finally divide 
again, by vertical walls, making four central cells, which become 
at once the sperm cells. According to Belajeff the walls of the 
peripheral cells become dissolved finally, so that the sperm cells 
float free within the spore cavity. Each sperm cell forms a 
single coiled spermatozoid, which is more slender than that of 
Marattia, but like it is multiciliate. 

In microtome sections of the germinating spores of /. echino- 
spora, the walls of the peripheral cells were evident after the 
spermatozoids were completely formed, and there seems some 
doubt whether they are absorbed at all. Occasionally (Fig. 
310, D) the sperm-cells were divided into two separate groups 
as in Marsilia. 

The macrospores are very many times larger than the micro- 
spores, and are of the tetrahedral type instead of bilateral. 
They are nearly globular in form and show plainly the three 
converging ridges on the ventral surface. If the fresh spore 
is crushed in water, its contents appear milky, and microscopic 



540 



MOSSES AND FERNS 



CHAP. 



examination reveals numerous oil-drops and some starch- 
granules, mingled with roundish bodies of albuminous nature. 
The latter absorb water and swell up so that they look like free 
cells. 

The wall of the spore is viery thick. The perinium is thick 



E ^ 














■::..\ 



O 



^ X 

I S 

9^ H 



fa 



60 O « 

s 



and transparent in appearance, and in the species under con- 
sideration provided with short recurved spinules. The interior, 
in microtome sections, is filled with coarsely granular cytoplasm, 
which often appears spongy, owing no doubt to the dissolving 



XIV ISOETACE^ 541 

out of the oil. Scattered through the cytoplasm are round 
starch granules with a central hilum. The large nucleus lies 
in the basal part of the spore. It is broadly oval in outline, 
and the cytoplasm immediately about it is nearly free from large 
granules. Before germination begins there are few chro- 
mosomes, and the nucleolus does not stain readily. 

In /. laciistris (Farmer (2)) the primary nucleus is at the 
apex of the spore, and this is also the case in /. Malinverniana 
(Arnoldi (i)). 

After the spores have lain a few days in water, the nucleus 
increases in size, and then the nucleolus stains very intensely 
and the chromosomes become more conspicuous. The nucleus 
divides while still in its original position, and undergoes division 
in the usual way. A very evident cell plate is formed in the 
equator of the nuclear figure (Fig. 311, A), but no cell wall is 
found, and the result of the division is two large free nuclei. 
The next youngest stage observed (Fig. 311, B) had four free 
nuclei, which now had moved to the ventral side of the spore. 
These are very much smaller than the primary one, but are 
relatively richer in chromatin. They continue to divide until 
there are from about thirty to fifty free nuclei, but as yet no 
trace of cell division can be seen. Most of the nuclei lie in 
the ventral part of the spore, close to the outer wall, but an 
occasional one may be detected elsewhere. 

Cell division begins at the apex (ventral part) of the spore. 
At this time the cytoplasm stains more deeply than before, 
and sometimes extremely delicate threads may be detected, 
radiating from the nuclei and connecting adjacent ones (Fig. 
311, C). The first traces of the division walls appear simul- 
taneously between the nuclei in the form of cell plates composed 
of minute granules, probably of cellulose, which quickly coalesce 
and form a continuous membrane. In this way the upper part 
of the spore becomes transformed into a solid tissue (Fig. 312). 

The formation of the cell walls closely resembles that in 
Selaginclla. The primary cells, or areoles, are open in their 
inner faces, and it is not until the second nuclear division takes 
place that the inner cell wall is developed. (Arnoldi ( i ), Figs. 

5,6). 

The cell formation proceeds quickly toward the base of the 
spore, following the spore wall, so that for a time the central 
space remains undivided. The whole process recalls most 



542 



MOSSES AND FERNS 



CHAP. 



vividly the endosperm formation of most Angiosperms. On 
account of the extremely thin walls and dense contents of the 




Fig. 312. — Isoetes echinospora van Braunii. A, Longitudinal section through the apex 
of the female prothallium, showing the first cell formation, X300; B, similar sec- 
tion of a prothallium with the divisions completed and the first archegonium iar) 
already opened. 



young prothallial cells it is not easy to determine exactly when 
the whole spore cavity becomes filled up with cellular tissue. 



XIV ISOETACEJE 543 

Because of the greater number of free nuclei in the upper part 
of the spore, and their consequent close proximity, the cells 
are smaller than those in the central and basal parts of the pro- 
thallium. Sometimes the transition from this small-celled tissue 
to the large-celled tissue of the basal part is quite abrupt and 
the more noticeable as the upper cells are more transparent ; but 
there was nothing to indicate that this was in any way con- 
nected with the early divisions of the primary nucleus, and more 
often no such sudden transition was seen. 

Hofmeister's account of the coalescence of previously sepa- 
rate cells to form the prothallium was obviously based upon 
incorrect observation, and is not borne out by a study of sections 
of the germinating spore. 

The first archegonium is very early evident, generally be- 
fore the cell division is complete in the lower part of the spore. 
It occupies the apex of the prothallium, and the mother cell is 
distinguished by its large size and dense granular contents. 
It is simply one of the first-formed cells that soon ceases to 
divide, and as its neighbours divide rapidly the contrast between 
them becomes very marked. Whether seen from above or in 
longitudinal section, it generally is triangular, or nearly so. In 
the structure of the mature archegonium, Ophioglossum shows 
strong points of resemblance, -as do the Marattiacese, but the 
egg cell is much larger in Isoetes. 

The development of the archegonium corresponds almost 
exactly with that of Marattia, but the basal cell is always want- 
ing, and the first transverse wall separates the central cell from 
the cover cell. The first division in the inner cell is parallel 
with the base of the cover cell, and divides it into the primary 
canal cell and central cell. The contents of the three cells of 
which the archegonium is now composed are similar, and the 
nuclei large and distinct. The cover cell next divides into four 
by transverse walls (Fig. 311, E), and from these, as in Marat- 
tia, the four rows of cells of the neck are formed. The number 
in each row is usually four in the mature archegonium. The 
ventral canal cell, which like that of Maraftia extends the whole 
breadth of the central cell, is separated almost simultaneously 
with the appearance of the first transverse divisions in the neck 
cells. The neck canal cell has at first a single nucleus, which 
later divides, but there is no division wall formed. Although 
the number of cells in each row of the neck is usually greater 



544 



MOSSES AND FERNS 



CHAP. 



than in Marattia, the neck canal cell is shorter and extends but 
little between the neck cells (Fig. 313, B). 

The egg is very large, round or oval in form, and the 
nucleus contains a large nucleolus that stains very intensely, 
but otherwise shows little chromatin. The receptive spot is of 
unusual size, and occupies about one-third of the egg. It is 




Fig. 313. — Tsoetes echinospora van Braunii. Development of the archegonium, X500; 
o, the egg; v, ventral canal cell; h, neck canal cell; D, shows a two-celled embryo 
within the archegonium. 



almost hyaline, showing, however, a faint reticulate arrange- 
ment of fine granules ; the lower portion of the egg is filled with 
granules that stain strongly. 

In /. lacustris, according to Hofmeister, only one arche- 
gonium is formed at first, and if this is fertilised, no others are 
produced; but in /. echinospora, even before the first arche- 
gonium is complete, two others begin to develop and reach ma- 
turity shortly after the first, whether the latter is fertilised or 



XIV ISOETACEJE 545 

not. In case all of these primary archegonia prove abortive, a 
small number, apparently not more than five or six, may be 
formed subsequently ; but so far as my observations go, the pro- 
duction of archegonia is limited, as is the growth of the pro- 
thallium itself.^ 

The development of the prothallium goes on without any 
increase in size, until the first archegonium is nearly complete, 
about which time the spore opens along the line of the three 
ventral ridges, and the upper part of the enclosed prothallium 
is exposed, but projects but little beyond the opening. In case 
all the archegonia prove abortive, the prothallium continues 
to grow until the reserve food material is used up, but then dies, 
as no chlorophyll is developed in its cells, and only in very rare 
instances are rhizoids formed. 

Miss Lyon (3) figures a longitudinal division of the neck 
canal cell in /. laciistris, and Arnold! (i) states that a similar 
division may occur in /. Malinrcrniana. 

The Embryo 

Besides the earlier account of Hofmeister, Kienitz-Gerloff 
(6) and Farmer (2) have made some investigations upon the 
embryogeny of /. laciistris, which correspond closely, so far as 
they go, with my ow^n on /. echinospora. 

The youngest embryos seen by me had the first division wall 
complete (Fig. 313, D). This is transverse, but more or less 
inclined to the axis of the archegonium. The nuclei of the two 
cells are large and contain several chromatin masses. The sec- 
ond division in the epibasal and hypobasal cells does not always 
occur simultaneously, the low^r half sometimes dividing before 
the upper one, and at times the second walls are at right angles 
instead of in the same plane. Of the quadrants thus formed, 
the two low^er form the foot, and the two upper ones the cotyle- 
don and primary root. The stem apex arises secondarily at a 
later period, and probably belongs to the same quadrant as the 
root; but as it does not project at all, and is not certainly recog- 
nisable until after the boundaries between the quadrants are no 
longer evident, this cannot be positively asserted. 

Sometimes the quadrants divide into nearly equal octants, 

* In old prothallia of /. laciistris according to Kienitz-Gerloff (6), there 
may be 20 to 30 archegonia. 

35 



546 



MOSSES AND FERNS 



CHAP. 



but in several young embryos examined, no definite octant walls 
were present, at least in the upper octants, but whether this 
is a common occurrence would be difficult to say. The next 
divisions in the embryo resemble those in Marattia, and as in the 
latter it may be said that the young members of the embryo 
grow for a short time from an apical cell, inasmuch as the tetra- 
hedral octants at first have segments cut off parallel with the 
basal, quadrant, and octant walls, leaving an outer cell (Fig. 
314, A) that still retains its original form; but very soon peri- 




FiG. 3i4.^A, An embryo of I. echinospora var. Braunii, with unusually regular 
divisions, X450; B, a much older one, still enclosed within the prothallium, XiSo; 
ar, archegonia. 



clinal walls arise in this cell in each quadrant, and it is no longer 
recognisable as an apical cell, and from this time the apex of the 
young member grows from a group of initial cells. 

Up to this time the embryo has increased but little in size, 
and retains the globular or oval form of the tgg. It now 
elongates in the direction of the basal wall, and soon after, the 
cotyledon and primary root become differentiated. The axis 
of the former coincides with the plane of the basal wall, and it 



XIV 



ISOETACE^ 



547 



approaches more or less the vertical as the latter is more or less 
inclined. Occasionally the basal wall is so nearly vertical that 
the cotyledon grows upright and penetrates the neck of the 
archegonium at right angles to its ordinary position. At the 
base of the leaf at this stage a single cell, larger than its neigh- 
bours, may often be seen (Fig. 315, A, I). This is the mother 
cell of the ligule, found in all the leaves. This cell projects, 







D 



B 






Fig. 315. — Development of the embryo in I. echinospora var. Braunii. A, Median longi- 
tudinal section: of a young embryo; B, four horizontal sections of a younger one; 
C, two vertical transverse sections of an older embryo; /, the ligula, X300. 



and as the leaf grows divides regularly by walls in a manner 
compared by Hofmeister to the divisions in the gemmae of 
Marchantia. It finally forms a scale-like appendage about 
twelve cells in length by as many in breadth. 

Almost coincident with the first appearance of the ligule 
a depression is evident, which separates the bases of the cotyle- 
don and root. The base of the latter, which now begins also to 



54« 



MOSSES AND FERNS 



CHAP. 



grow in length, projects in the form of a semi-circular ridge that 
grows rapidly and forms a sheath about the ligule and the base 
of the cotyledon (Fig. 317, v). The growth of this sheath is 
marginal, and continues until a deep cleft is formed. A num- 
ber of cells at the bottom of the latter between the sheath and the 
leaf base constitute the stem apex. As they differ in appear- 
ance in no wise from the neighbouring cells, it is quite impossible 




I. 




Fig. 3l6.^Three successive horizontal sections of a somewhat advanced embryo of 
I, echinospora var. Braunii, X260; R, root; cot, cotyledon; st, stem; /, ligula. 



to say just how many of them properly belong to the stem. So 
far as can be judged, the origin of the growing point of the 
stem is strictly secondary, and almost exactly like that of many 
Monocotyledons.^ 

Longitudinal sections of the embryo, when root and leaf are 

^ See Hanstein's figures of Alisma, for example, in Goebel's Outlines, 
Fig. 332. 



XIV ISOETACE^ 549 

first clearly recognisable, show that the foot is not clearly de- 
fined, as the basal wall early becomes indistinguishable from the 
displacement due to rapid cell division in the axis of the embryo. 
It projects but little, and the cells are not noticeably larger than 
those of the cotyledon and root. 

As the cotyledon lengthens it becomes somewhat flattened, 
and in the later stages its increase in length is due entirely to 
basal growth. Even in very young embryos a distinct epi- 
dermis is evident in the leaf, and about the time that the ligule 
is formed the first trace of the vascular "tissue appears. This 
consists of a bundle of narrow procambium cells, which lie so 
near the centre of the embryo that it is impossible to assign it 




Fig. 317.— Median longitudinal section of an embryo'of the same species shortly before 
the cotyledon breaks through the prothallium; lettering as in the preceding, X300. 

certainly to either root or leaf; indeed it sometimes seems to 
belong to one quadrant, sometimes to the other. From it the 
development of the axial bundles of cotyledon and root pro- 
ceeds, and by it they are directly united. The section of the 
central cylinder of the leaf is somewhat elliptical, and it does not 
extend entirely to the end. Its limits are clearly defined from 
the periblem, in which the divisions are mainly transverse and 
the cells arranged in regular rows. 

The primary xylem consists of small spiral and annular 
tracheids at the base of the leaf, and from these the formation 
of similar ones proceeds towards the tip. Their number is 
small, even in the full-grown leaf, and they are the only difTer- 



550 



MOSSES AND FERNS 



CHAP. 



entiated elements, the rest of the bundle showing only elongated 
parenchyma, much like the original procambium cells. 

The axis of growth of the primary root usually coincides 
with that of the cotyledon, but this is not always the case. In 





Fig. 318.— a, Median section of a young sporophyte with the second leaf U already 
formed; r^, second root; st, stem-apex, X150; B, cross-section near the base of the 
cotyledon, showing the intercellular spaces i and the second leaf U surrounded by 
the sheath v at the base of the cotyledon; /, the ligule of the cotyledon, X300. 



the very young root (Fig. 317, R) the end is covered with a 
layer of cells continuous with the epidermis of the rest of the 
embryo. Beneath are two layers of cells concentric with the 



XIV ISOETACEJE 55i 

epidermis. From the inner one arises the initial cell (or cells?) 
of the plerome, which soon becomes well defined and connected 
with the primary strand of procambium in the axis of the em- 
bryo. It is quite possible that here, as in the older roots, a' 
single initial cell is present in the plerome, but this is not cer- 
tain. The layer of cells immediately below the primary epi- 
dermis is the" initial meristem for all the tissues of the root 
except the plerome. The primary epidermis later divides into 
two concentric layers which take no further part in the growth 
of the root except as they join the outer layers of the root-cap. 

From the layer above the plerome initial, additions are made 
at regular intervals to the root-cap, and these layers remain one 
cell thick, so that the stratification is very marked. At the 
apex of the root there is no separation of dermatogen and peri- 
blem, which are first differentiated back of the apex. The pri- 
mary xylem consists of very delicate spiral tracheids formed at 
the base of the root at the same time that the first ones appear 
in the leaf. 

The foot increases much in size as the leaf and root develop, 
and its superficial cells become much enlarged and encroach 
upon the large cells of the prothallium, whose contents are 
gradually absorbed by it. 

The cotyledon is at first composed of compact tissue, whicH 
during its rapid elongation separates in places, and forms a sys- 
tem of large intercellular spaces. There are two rows of very 
large ones, forming two broad air-chambers extending the 
whole length of the leaf, but these are interrupted at intervals 
by imperfect partitions composed of single layers of cells. In 
the root there are similar lacunae, but they are smaller and less 
regularly arranged. 

The growing embryo is for a long time covered by the pro- 
thallial tissue, which in the upper part continues to grow with 
it; but finally cotyledon and root break through, the former 
growing upward, the root bending down and anchoring the 
young sporophyte in the mud. Owing to the large air-spaces 
the cotyledon is lighter than the water, and always stands ver- 
tically, whether the original position was vertical or horizontal. 
In the latter case the plant appears to be attached laterally to the 
prothallium, and the stem apex, which when first formed stands 
almost vertically, now assumes the horizontal position which 
it has in the older sporophyte. 



552 



MOSSES AND FERNS 



CHAP. 



About the time that the young sporophyte breaks through 
the prothalHum, the second leaf begins to develop. The grow- 
ing point (Fig. 318, st) now lies in the groove between the 
base of the root and the cotyledon, and its nearly flat surface 
is at right angles to the axis of the latter. The second leaf 
(L^) arises as a slight elevation on the side of the stem directly 
opposite the cotyledon. From the first it is multicellular, and 
its growth is entirely like that of the cotyledon, which it other- 
wise resembles in all respects. Almost as soon as the leaf is 
evident at all, a strand of procambium cells is formed running 
from the junction of the cotyledon and first root, and is con- 
tinued into the second leaf as its plerome. 

The second root develops 
from the base of the second leaf 
in the immediate vicinity of the 
/ common fibrovascular bundle, 
and is formed about the time 
that the leaf begins to elongate. 
A group of cells here begins to 
multiply actively, and very soon 
shows a division into the initials 
of the tissue systems of the 
young root. From this time 
the growth proceeds as in the 
primary root, and it finally 
breaks through the overlying 
tissues. 

The stem has no vascular 
bundle apart from the common 
bundle formed from the coales- 
cence of the bases of the bundles from the leaves and roots. In 
all the later-formed leaves and roots there is but a single axial 
bundle. In the leaves this is decidedly collateral in form with 
the poorly-developed xylem upon the inner (upper) side. Ex- 
cept for their larger size, and their having usually four instead 
of two air-channels, the later leaves resemble in all respects those 
first formed. 

The development of the young plant was not followed be- 
yond the appearance of the third leaf, but it probably in its later 
history corresponds to /. lacustris. In the latter, according to 
Hofmeister ((i), p. 354), the opposite arrangement of the 




Fig. 319.— Longitudinal section of the 
second root, X525; PI, plerome. 



XIV 



I SORT AC EM 



553 



leaves continues up to about the eighth, when the {■ divergence 
is replaced successively by |, |^ |, -f^, and -ij, which is the con- 
dition in the fully-developed sporophyte. 

The Adult Sporophyte (Sadebeck (p)) 

The structure of the mature sporophyte has been the sub- 
ject of repeated investigations, among the most recent being 

B. 




Fig. 320. — A, B, Isoetes echinospora. A, Section of fully developed leaf, X15; B, 
vascular bundle of the leaf, X about 200; C, part of a transverse section of the 
stem of I, lacustris; sp, starch-bearing cortical cells; m, meristematic zone; h, 
tracheids; hd, tissue of the central region (C after Potonie). 

those of Farmer (2) and Scott (2), who made a most careful 
examination of the vegetative organs in /. lacustris and /. hys- 
trix. The thick, very short stem has a central vascular bundle, 
which as in the young plant is made up of the united leaf-traces, 
and there is no strictly cauline portion, as Hegelmaier ( i ) and 



554 MOSSES AND FERNS chap. 

Bruchmann (i) assert. Scott (2), however, states that in /. 
hystrix, there is a short, cauhne stele distinct from the leaf 
traces. 

This central cylinder is composed of very short tracheids, 
with spiral and reticulate markings, mixed with similarly- 
shaped cells with thin walls. Surrounding this xylem cylinder 
is a layer of cells, which Farmer calls the "prismatic layer.'* 
This, according to Russow ((i), p. 139), is continuous with 
the phloem of the leaf-traces, and he regards it as the phloem of 
the stem bundle. Outside of this prismatic layer is a zone of 
meristematic cells, which form the "cambium." The cells of 
this zone are like those of the cambium of Boytrychium or of 
the Spermatophytes, and like these new cells are formed on both 
sides; but those formed upon the outside remain parenchyma- 
tous and are gradually thrown off with the dead outer cortex. 
Those upon the inner side develop into the prismatic cells, 
mingled with which are cells very like the tracheids, except 
that they retain to some extent their protoplasmic contents. 
These cells are arranged in more or less well-marked zones, and 
possibly mark the limits of each year's growth. It will be seen 
from what has been stated that while a true secondary thick- 
ening of the stem occurs in Isoetes, it is quite different from 
that in Botrychiiim, which closely resembles the normal thicken- 
ing of the coniferous or dicotyledonous stem. It has been com- 
pared to that found in Yucca or Draccena, and this perhaps is 
more nearly like it. However, as the development of cambium 
and secondary thickening have evidently occurred independ- 
ently in very widely separated groups of plants, it is quite likely 
that we have here one more instance quite unconnected with the 
same phenomenon elsewhere. 

The leaves, as already stated, differ but little from those of 
the young plant. The vascular bundle is somewhat better 
developed, but remains very simple, with only a few rows of 
tracheids fully developed. The vascular bundle of the leaf is 
better developed at the base of the leaf, and especially behind 
the sporangium ( Smith ( i ) ) . 

The phloem remains undifferentiated, and no perfect sieve- 
tubes can be detected. The phloem lies upon the outer side of 
the xylem, but shows a tendency to extend round toward the 
upper side. Of the Filicinese, Ophioglossiini comes the nearest 
to it in the structure of the bundles. The air-channels are four 



XIV 



ISOETACEJE 



555 



in number in the fully-developed leaf, and the diaphragms 
across them more regular and complete. Instead of being 
throughout but one cell thick, as in the first leaves, they are 
thicker at the edges, so that in section they appear biconcave. 
In the older leaves the broad sheath at the base is much better 
developed, and the over-lapping leaf bases give the whole stem 
much the appearance of the scaly bullj of many Monocotyledons. 




Fig. izx.-^Isoetes lacustris. Section of root-apex, showing dichotomy, X about 190 

(after Bruchmann). 



In all the terrestrial species, and those that are but partially im- 
mersed, the leaves are provided with numerous stomata of the 
ordinary form ; but in some of the submersed species these are 
partially or entirely wanting. The development of the ligule 
also varies, being very much greater in the terrestrial species, 
where it may possibly be an organ of protection for the younger 
leaves. 

The ligule in its fully developed condition (Smith (i)) 
shows four portions: i, a sheath of glandular appearing cells 
at its base; 2, the "glossopodium," consisting of a band of large 
empty cells, above which is (3) the main portion of the ligule, 
composed of small cells containing protoplasm ; 4, the apex, 
composed of dead cells. 



556 MOSSES AND FERNS chap. 

Hofmeister states that in /. lacustris the first sporangia are 
not developed until the fourth year from the time the young 
sporophyte is first formed. The sporophylls begin to form in 
the third year, but it is a year more before the sporangia are 
complete. From this time on, the regular succession of sporo- 
phylls and sterile leaves continues. 

There has been much disagreement as to the method of 
growth in the root. The earlier observers attributed to it a 
single apical cell, not essentially different from that of the true 
Ferns; this was shown to be incorrect by Bruchmann (i) and 
Kienitz-Gerloff (6), but Farmer (2) claims that none of these 
have correctly described the structure of the larger roots, which 
differs somewhat from that of the earlier ones. According to 
the latter observer there is always a single initial for the plerome, 
and above this two layers of meristem, one giving rise to the 
inner cortex, the other to the outer cortex, as well as to the epi- 
dermis and root-cap. The fibrovascular bundle is monarch, 
like that of Ophioglossum vulgatum, and the phloem becomes 
differentiated before the xylem elements are evident. 

The later roots arise much as the second one does in the 
young plant, but the rudiment is more deeply seated. The 
roots are arranged in /. lacustris in four rows, two correspond- 
ing to each furrow (Van Tieghem (5)). According to 
Bruchmann the first evidence of a forming root is a single cell 
of the cortical tissue lying a short distance outside of the leaf- 
trace. This, however, cannot be looked upon as the apical cell, 
as it only gives rise to calyptrogen and dermatogen. The peri- 
blem and plerome arise from the cells lying immediately 
below it. 

The branching of the roots is a genuine dichotomy, and has 
also been carefully studied by Bruchmann (Fig. 321). He 
states that the process begins by a longitudinal division of the 
plerome initial, and each of the new initials at once begins to 
form a separate plerome. The overlying tissues are passive, 
and their divisions are governed by the growth of the two 
plerome strands. 

The Sporangium 

The development of the sporangium has been studied by 
Goebel (3), and more recently by Bower (15), and Wilson- 
Smith (i). Each leaf, except the imperfect ones that sepa- 



XIV 



ISOETACE^' 



557 



rate the sporophylls of successive years, bears a single very large 
sporangium, situated upon the inner surface of the expanded 
base. 

According to Goebel (3) the young sporangium consists of 
an elongated elevation composed of cells which have divided by 
periclinal walls; but both Bower (15) and Smith (i) state that 
it can be traced back to a small group of strictly superficial cells 
which later undergo periclinal divisions. 




Fig. 322. — Isoetes echinospora. A, section of young sporophyll, X325; /, ligule; the 
sporangial cells have the nuclei shown. B, section of part of a young macro- 
sporangium, X325; the sporogenous cells have the nuclei shown. C, cross-section 
. of the base of a young sporophyll, with microsporangium, X25; v, the velum; vb, 
vascular bundle; the trabeculae are left unshaded. (After Wilson-Smith). 



The very complete account of the development of the spo- 
rangium of /. echinospora made by Wilson-Smith (i) differs 
in some important details from that of Goebel. The first peri- 
clinal division, while it may separate a definite parietal layer, 
does not, as a rule, do this; but there are further periclinal 
divisions in the superficial layer of cells which add to the spo- 
rogenous tissue, much as is the case in Equisetum and Ophio- 
glossiim. There is not, therefore, the early and definite segre- 
gation of the archesporium described by Goebel, nor do the 
archesporial cells remain independent, as Goebel states is the 
case in /. lacttstris. 

Wilson-Smith finds a complete absence of the regular 



558 MOSSES AND FERNS chap. 

arrangement of the cells described by Goebel. He says (1. c, 
p. 241), ''I am forced to conclude that the sporangium-of Isoetes 
(at least of /. echinospora and /. Engelmanni) just as the 
microsporangium of Angiosperms, grows as a unit, and not as 
a number of individual segments." 

The velum appears very early and is apparently developed 
directly from a part of the sporangium-fundament — indeed it 
looks as if in some cases it actually contributed to the sporoge- 
nous tissue. The velum reaches its full development before the 
rest of the sporangium does. In certain species, some of its 
cells, as well as those of the adjacent leaf-tissues, may become 
lignified and show spiral and annular thickenings. 

In their early stages, there is no difference between micro- 
and macrosporangia. Wilson-Smith could find no indication 
in the species investigated by him, of the early differentiation 
of the two kinds of sporangia described by the early investi- 
gators. In both macro- and microsporangia, divisions occur 
in all directions, resulting in a very large mass of potential spo- 
rogenous tissue. There is later, however, a differentiation of 
the archesporial tissue into fertile and sterile areas, the latter 
forming later the "trabeculse." 

About the time that the last cell-divisions are taking place In 
the archesporial tissue, certain regions divide less actively and 
react less strongly to stains. These relatively inactive regions 
are the sterile ones, and from them are developed the sporan- 
gium wall, the trabeculse and tapetum, while the. rest of the 
archesporial tissue, at least in the microsporangium, develops 
spores. 

The trabeculse are more or less irregular masses of tissue, 
not forming definite partitions, although they may anastomose 
more or less freely (Fig. 322, C). The cells of the trabecula 
become flattened and extended by the subsequent growth of the 
sporangium, and lose to a great extent their protoplasmic con- 
tents, so that they soon become clearly separated from the inter- 
vening sporogenous cells. The trabeculse later undergo a fur- 
ther differentiation into a layer next the sporogenous cells, this 
outer layer constituting the tapetum, and an inner mass of much 
larger and more colourless cells, the trabecular proper. 

The young tapetal cells do not stain strongly, but later, 
when they presumably become active in supplying the young 
spores with food, they stain even more strongly than the spo- 



XIV ISOETACEJE 559 

rogenous cells. As in Lycopodium and Selaginella, the tapetal 
cells remain intact, instead of being broken down as they usually 
are in the Ferns and Eqnisctum. 

In the microsporangium all the sporogenous cells divide, 
the divisions being successive and usually resulting in spores of 
the ''bilateral" type, although tetrahedral spores are sometimes 
formed. The number of spores in each sporangium is very 
great. In /. echinospora, it ranges from 150,000 to 300,000. 

The Macrosporangium 

The earliest stages of both types of sporangium are alike, 
but the macrosporangia are recognisable as such earlier than 
the microsporangia. In the former, before any distinction of 
fertile and sterile tissue is evident, certain cells become notice- 
ably larger than their neighbours, and enter into competition, as 
it v^ere, to become the spore mother cells. There is apparently 
no rule as to either the number or position of these potential 
mother cells ; but sooner or later some of them outstrip their 
competitors, become very large, and ultimately divide into the 
four macrospores. 

The formation of the trabeculse and tapetum is essentially 
the same as in the microsporangium ; but the trabeculse are fewer 
and more massive, and the tapetum is several cells in thickness. 
The unsuccessful sporogenous cells probably are used up in the 
further development of the growing spores. 

The further development of the macrospore has been studied 
in /. Diirieui by Fitting ( i ) . Preliminary to the first nuclear 
division in the mother cell, whose membrane consists of a pec- 
tose-compound and not cellulose, there is a division of the starch 
granules into two groups which divide again, and the four 
starch masses arrange themselves tetrad-wise in a way that 
recalls the behaviour of the cell contents in the dividing spore 
mother cells of Anthoceros. The four nuclei resulting from the 
repeated division of the primary nucleus are in close contact 
with the four starch masses, and there then follows the simul- 
taneous formation of cell plates between the nuclei. The cell 
plates are replaced by the cell walls which separate the four 
young tetrahedral macrospores. 

The protoplast of each young spore secretes about itself a 
special membrane from which is later developed the characteris- 



56o MOSSES AND FERNS chap. 

tic perispore. Within the special membrane is developed a sec- 
ond membrane — exospore — which later shows a division into 
three layers. Within the exospore the mesospore and endo- 
spore arise very much as in Selaginella, which Isoetes further 
resembles in the separation of the mesospore from the protoplast 
and from the exospore, although this is less conspicuous